HX64119190 
RC78  .D28  Localization  by  X-ra 


KC7S  DZS 

College  of  ^Ijpgtdang  anb  burgeons 
ilibrarp 


G-lZ-to/ 


Pa.u.1  B.  Hocter  Inc 


LOCALIZATION    BY   X    RAYS   AND 
STEREOSCOPY 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

Open  Knowledge  Commons 


http://www.archive.org/details/localizationbyxrOOdavi 


A  Convenient  Procedure  for  Viewing  the  Stereoscopic 
Illustrations  in  this  Volume, 

The  stereoscope  employed  is  one  commonly  supplied  by  opticians  with  the 
end-piece  sawn  off.  The  focus  is  easily  adjusted  by  arranging  the 
distance  at  which  the  book  is  held  from  the  observer. 

Fvontispiece. 


LOCALIZATION 


BY 


X    RAYS 
AND    STEREOSCOPY 


SIR   JAMES    MACKENZIE    DAVIDSON 

M.B.,  CM.  Aberd. 

CONSULTING   MEDICAL   OFFICER,    ROENTGEN    RAV   DEPARTMENT,    ROYAL    LONDON   OPHTHALMIC 

HOSl'ITAL,    AND    X-RAY   DEPARTMENT,    CHARING   CROSS    HOSPITAL  ; 

FELLOW,    PHYSICAL   SOCIETY  ; 

PRESIDENT,    RADIOLOGY   SECTION,    SEVENTEENTH    INTERNATIONAL   CONGRESS    OF    MEDICINE 


WITH  35  STEREOSCOPIC   ILLUSTRATIONS   ON    SPECIAL   PLATES, 
AND  OTHER  FIGURES  IN  THE  TEXT 


PAUL    B.     HOEBER 

67    &    69    EAST    59TH    STREET 

NEW    YORK 

1 916 


{Printed  in  England'] 


u'v 


^ 

\\-^^- 


PREFACE 

It  is  nearly  twenty  years  since  the  author  first  de- 
scribed, in  the  medical  press,  the  system  of  exact 
localization  by  means  of  X  rays  which  is  mainly  the 
theme  of  this  volume.  The  present  appalling  war, 
with  its  enormous  number  of  casualties,  made  it  seem 
likely  that  a  more  detailed  description  of  the  method 
in  book  form  would  be  of  some  service  to  those  engaged 
in  X-ray  work  among  the  wounded.  No  attempt  has 
been  made  in  these  pages  to  cover  the  vast  ground  of 
X-ray  work  in  general;  the  aim  has  been  merely  to 
bring  together  a  number  of  practical  points  connected 
with  the  author's  personal  work.  The  system  he 
advocates  has  stood  the  test  of  time,  but  it  has  also 
shown  itself  adaptable  to  the  more  rapid  procedure 
which  is  demanded,  and  the  simplifications  which  have 
been  introduced  into  the  original  method  will  be  found 
fully  described  in  the  body  of  this  book. 

The  author  would  direct  special  attention  to  the 
final  chapter,  which  deals  with  the  precise  localization 
of  foreign  bodies  in  eyeball  and  orbit,  for  he  trusts  that 
this  application  of  X  rays  may  be  extended.  As  every 
ophthalmic  surgeon  knows,  foreign  bodies  in  the  eye- 
ball and  orbit  are  ever  with  us.  At  present,  owing  to 
hand-grenade  warfare,  such  cases  are  occurring  in  very 
large  numbers,  but  in  civil  life,  especially  in  engineering 
workshops  and  various  industrial  concerns,  these  cases 
are  constantly  met  with;  and  very  often  it  happens 
that  the  eye  can  be  saved  if — but  only  if — the  exact 
position  of  the  foreign  body  is  known,  so  that  it  ma}/  be 
extracted  without  difficulty. 


vi  PREFACE 

As  far  as  possible,  the  practical  and  utilitarian  aspect 
of  the  subject  has  been  adhered  to,  and  any  theoretical 
considerations  have  been  introduced  only  in  so  far  as 
they  have  a  direct  bearing  on  the  practical  side  of  the 
work.  Probably  no  one  is  quite  satisfied  with  the 
result  of  his  labours,  and  the  author  is  fully  aware  of 
the  many  shortcomings  of  this  little  volume;  at  the 
same  time,  he  hopes  that  it  may  prove  of  some  use  at 
the  present  juncture. 

Special  care  has  been  given  to  the  illustrations,  the 
great  majority  of  which  are  from  the  author's  stereo- 
scopic photographs.  A  book  which  advocated  stereo- 
scop3^  could  hardly  be  otherwise  illustrated  than  by 
stereoscopic  methods ;  in  fact,  many  of  the  illustrations 
in  this  book  rely  for  their  value  entirely  upon  being 
viewed  stereoscopicaily ;  otherwise  they  are  meaning- 
less. The  author  recommends  the  viewing  procedure 
illustrated  in  the  frontispiece.  The  instrument  held 
in  the  hand  consists  of  a  stereoscope  minus  the  ordin- 
ary projection  for  holding  the  print;  it  is  cut  off  short 
at  the  end  of  the  T-piece  which  separates  the  lenses, 
and  will  be  found  convenient  and  economical  for  use 
in  the  case  of  stereoscopic  book  illustrations,  and,  in- 
deed, for  ordinary  prints  and  transparencies.  It  is 
supplied  by  Messrs.  Hinton  &  Co.,  of  38,  Bedford 
Street,  Strand,  London,  W.C. 

The  author's  thanks  are  due  to  Messrs.  W.  Watson 
&  Sons,  Ltd.,  for  the  loan  of  the  plates  on  pages  23,  27, 
and  34;  and  to  Mr.  A.  W.  Bond  for  the  illustration  of 
the  telephone  attachment  on  page  57.  He  has  also 
to  thank  Mr.  Harry  Cooper  for  his  most  valuable 
assistance  in  the  preparation  of  this  little  book — 
indeed,  without  his  aid  and  co-operation  it  might  never 
have  been  completed. 

March,   igi6. 


CONTENTS 


CHAPTER  PAGE 

I.    THE    X-RAY   TUBE     -                 -                 -                 -                 -                 -  I 

II.    SECONDARY    RAYS   AND    X-RAY    PROTECTION                -                 -  7 

III.  X-RAY    STEREOSCOPY  -  -  -  -  "14 

IV.  RAPID    X-RAY    LOCALIZATION                -                 -                 -                 -  22 
V.    THE    CROSS-THREAD    METHOD               -                 -                 -                 "29 

VI.    PRECISE    localization:    FURTHER   CONSIDERATIONS              -  42 

VII.    LOCALIZATION  OF  FOREIGN  BODIES  IN  EYEBALL  AND  ORBIT  47 

APPENDIX 

I.    TELEPHONE  ATTACHMENT  IN  SURGERY              -                 -  55 

II.    THE  ELECTRO-MAGNET  AS  AN  AID  TO  LOCALIZATION     -  59 

III.  LOCALIZATION  FROM  A  SINGLE  PHOTOGRAPH                  -  61 

IV.  THE  RECTIFICATION  OF   THE    CURRENT    SUPPLIED    TO 

THE  X-RAY  TUBE      -                 -                -                -                 -  64 

V.    RULES   FOR   THE   PROTECTION    OF   X-RAY   OPERATORS  69 

VI.    PLATES  ILLUSTRATING  SPECIAL  CASES  (FROM  STEREO- 
SCOPIC X-RAY  PHOTOGRAPHS)             following  page  70 


INDEX 


71 


LIST   OF   ILLUSTRATIONS 


A  viewing  stereoscope 


Frontisp  iece 


1.  X-ray  tube  in  action  .         .         .         . 

2.  Diagram  of  cathode  rays 

3.  Pinhole  photographs  of  tube  foci 

4.  Tube  with  wire  cross  in  position 

5.  X-ray  image  of  wire  cross 

6.  Pinhole  photograph  of  anode — front  view   - 

7.  Pinhole  photograph  of  anode — end-on  view 

8.  Tube  with  mass  of  lead  suspended  in  front 

9.  X-ray  shadow  of  netting :  result  of  second- 

ary-ray action        .  .  .  .  - 

10.  Tube  surface  bisected  by  strip  of  lead 

11.  Double    image    obtained    with    tube    thus 

bisected        ------ 

12.  Quadruple  image  obtained  by  placing  lead 

cross  in  front  of  tube      -         -         -         - 

13.  X-ray  image :  tubular  stop  employed 

14.  X-ray  image :  without  tubular  stop 

15.  Diagram  of  secondary  rays 

16.  Stereoscopic  view  of  pair  of  scissors     -        - 

17.  Wheatstone  stereoscope     -         -         -         - 

18.  Method  of  viewing  with  Wheatstone  stereo- 

scope  ------- 

19.  Method  of  viewing  with  Brewster  stereo- 

scope   ------- 

ix 


I. 

I. 
II. 
III. 
III. 
IV. 
IV. 

V. 

V. 
VI. 

VI. 

VII. 
VIII. 
VIII. 

IX. 

IX. 

X. 


facing 


10 
10 
10 

9 

16 
16 

18 


X. 


LIST  OF  ILLUSTRATIONS 


20.  New  X-ray  couch  -         -         - 

21.  Screen  localizer  with  hand  fluoroscope 

22.  Screen  locaUzer  without  fluoroscope 

23.  Diagram  illustrating  parallel  and  central 

projection  -         -     .    - 

24.  Diagram  illustrating  planes  of  reference  - 

25.  The  cross-thread  localizer        -         .         - 

26.  Double-exposure  photograph  to  illustrate 

planes  of  reference      .         -         .         - 

27.  A  and    B.     Diagram  to   illustrate  cross- 

thread  method   -         -         -         - 

28.  Head -rest  for  eye  localization 

29.  Shadow  of  intersecting  piano  wires  to  illus- 

trate accurate  centring  of  anode 

30.  Head-rest     for     eye     localization     (with 

patient)     ------ 

31.  Side  view  of  head-rest    -         -         -         - 

32.  Loop  of  mre  to  keep  eye  immobile 

33.  Method  of  fastening  indicator  wire  to  lower 

eyelid        ------ 

34.  X-ray  photograph  of  eye,   with  loop  in 

position      ------ 

35.  Double-exposure  photograph  of  model  eye 

with  planes  of  reference       .  .          - 

36.  Double-exposure  photograph  of  head -rest 

with  head  in  position,  showing  planes  of 
reference    ------ 

37.  Ditto  (viewed  from  opposite  side)    - 

38.  Action  of  telephone  attachment 

38A.  Diagram  showing  tube  displacement     - 


PLATE  PAGE 

-  23 

-  27 

-  27 

-  30 

-  31 

-  34 

-  37 

-  39 
XI.    facing  48 


XL 


48 


XII. 

„   48 

XII. 

„   48 

XIII. 

„    50 

XIII. 

„     50 

XIV. 

„    50 

XIV. 

„     50 

XV. 

>     52 

XV. 

.     52 

57 

J 

„       62 

PLATES  ILLUSTRATING  SPECIAL  CASES 

(^From  stereoscopic  X-ray  photographs.) 

39.  Fragment  of  bomb  in  knee     .  -  -         -          - 

40.  Rifle  bullet  near  lumbar  vertebra  -         -         -         - 


PLATE 

XVI. 
XVI. 


LIST  OF  ILLUSTRATIONS 


XI 


PIG. 
41. 

42. 

4j- 
44- 
45- 
46. 

47- 
48. 
49. 
50- 
51- 
5-- 
53- 
54- 
55- 
56. 

57- 

58. 

59- 
60. 

61. 


Gunshot  wound  in  foot          -----  X\II. 

Needle  lodged  in  knee  -         .         .         -         -         -  X\II. 

Fracture  of  jaw  -------  X\  III. 

Broken  needle  in  foot             -----  X\  III. 

Fragment  of  shell  in  thigh    -----  XIX. 

Bullet  located  between  scapula  and  ribs           -         -  XIX. 

Female  peMs  with  catheterized  ureter  -         -         -  XX. 

Teeth,  antrum,  and  frontal  sinuses          -          -          -  XX. 

Shrapnel  bullet  above  hip-joint      .         -         -         -  XXI. 

Piece  of  shell  near  trochanter  major        -         -         -  XXI. 

Eye,  wdth  embedded  fragments  of  lead  -         -         -  XXII. 

Fragment  of  high-explosive  shell  in  orbit         -         -  XXII. 

Minute  metal  particles  in  eyeball  -         -         -         -  XXIII. 

Shot  external  to  sclerotic      -----  XXIII. 

Debris  in  outer  part  of  orbit,  result  of  buUet  wound  -  XXIV. 

Shot  in  upper  and  inner  part  of  orbit     -         -         -  XXIV. 

Piece  of  high -explosive  sheU  in  orbit       -         -         -  XXV. 

Metal  particles  inside  eyebaU          ...         -  XXV. 

CooUdge  tube  in  action  (stereoscopic  \aew)      -          -  XXVI. 

Pinhole  photograph  of  CooHdge  tube     -          -          -  XXVL 

Pinhole  photograph  of  ordinary  X-ray  tube    -          -  XX\T. 


LOCALIZATION    BY    X    RAYS 
AND   STEREOSCOPY 


CHAPTER  I 

THE   X-RAY   TUBE 

Introduction. — The  importance  of  being  able  to 
ascertain  the  exact  position  of  bullets  and  fragments 
of  shell  lodged  in  the  tissues  of  the  human  body 
needs  no  insistence  at  the  time  of  writing,  when  an 
appalling  number  of  wounded  are  being  returned 
from  the  seat  of  war.  Not  only  are  localization 
methods  essential  while  war  is  actually  in  progress, 
but  even  after  hostilities  have  ceased  many  cases 
are  bound  to  arise  in  which  fragments  of  metal,  whose 
extraction  was  not  at  first  thought  necessary  or  desir- 
able, will  be  found  to  give  trouble  and  require  to  be 
localized.  It  would  seem  that,  in  this  country  at  all 
events,  while  a  great  many  of  those  occupied  in  X-ray 
practice  can  produce  admirable  photographs,  they 
encounter  considerable  difhculty  in  localizing  with 
sufficient  exactness  the  position  of  the  foreign  body. 
It  has  occurred  to  the  author,  therefore,  that  having 
given  many  years  of  labour  to  this  subject  of  localiza- 
tion, he  may  usefully  offer  to  other  workers  in 
this  same  field  some  remarks  on  his  methods  and 
experiences. 


2       LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

It  is  assumed  that  the  reader  is  familiar  with  the 
ordinary  X-ray  outfit  and  its  working,  and  therefore 
a  dissertation  on  this  elementary  part. of  the  subject 
may  be  omitted  entirely.     There  are  several  excellent 
manuals    describing    in    detail    the    apparatus    and 
technique,  and  it  would  be  of  little  use  to  repeat,  in 
a  condensed  form,  what  can  be  found  so  fully  dealt 
with  already  in  these  publications.     So  far  as  this 
volume  is  concerned,  the  consideration  will  be  limited 
mainly  to  the  localization  of  foreign  bodies  by  methods 
of  precision,  to  stereoscopic  X-ray  work,  and  to  the 
highly  specialized  subject  of  localization  in  the  eyeball 
and  orbit.     Before  entering  upon  a  discussion  of  these 
subjects,  however,  it  is  necessary  to  pay  some  attention 
to  the  question  of  the  X-ray  tube  in  action  (Fig.  i) 
and  its  properties,  as  this  will  be  found  to  have  a 
practical  bearing  upon  the  successful  working  of  the 
localization  methods  to  be  considered  presently. 

The  X-Ray  Tube. — In  the  rapid  advance  of  modern 
physics,  many  points  have  been  elicited  which  are  of 
extreme  interest  to  those  who  have  to  handle  the 
X-ray  tube,  but  in  these  pages  the  characteristics  of 
the  rays  and  similar  questions  can  onty  be  discussed 
in  their  relation  to  practical  X-ray  work.  It  is 
necessary,  however,  to  bear  in  mind  the  internal 
construction  of  the  tube  and  its  adaptation  to  the 
energies  which  it  has  to  control.  The  cathode  rays, 
taking  origin  at  the  concave  cathode  terminal,  proceed 
in  straight  converging  lines  until  they  meet  at  a  fine 
point,  beyond  which  they  slowly  diverge  (Fig.  2). 
The  degree  of  convergence  depends  upon  the  curvature 
of  the  cathode  from  whence  they  take  their  departure. 
This  radiation  has  only  to  impinge  upon  a  target  to 
produce  X  rays  at  the  point  of  impact,  and  this  target 


PLATE  I 


Fig.  I. — Photograph  of  X-Ray  Tube  in  Action. 


Fig.  2. 


\To  face  p.  2. 


PLATE  II. 


Pinhole  Photograph  of  an  X-Ray  Tube  having  a  A'ery  Fine 
Focus,  in  which  the  Target  receives  the  Cathodal 
Stream  at  a  Very  Narrow  Point. 


Pinhole  Photograph  of  a  Tube  of  Larger  Focus. 

The  lowest  row  of  pinholes  represents  a  voltage  in  the  primarv  of  4,  the  middle 
row  of  8,  the  top  row  of  12  volts. 


Pinhole  Photograph,  taken  Obliquely,  of  the  X-Ray 
Producing  Surface  on  the  Target  of  a  Badly  Focussed 
Tube. 


Pinhole  Photograph  of  a  Badly  Focussed  Tube. 
Fig.  3. 


[To  face  p.  2. 


THE  X-RAY  TUBE  3 

is  SO  placed  as  to  meet  the  cathode  rays  somewhere 
near  their  focus.  It  seldom  happens,  however,  that 
a  tube  is  constructed  in  which  the  target — i.e.,  the 
anode  or  anticathode — is  arranged  to  meet  the  cathode 
stream  exactly  at  its  narrowest  point.  The  tube- 
makers  soon  discovered  that  if  the  anode  were  placed 
in  that  position  (Fig.  2,  position  marked  x),  the 
intensity  of  the  cathode-ray  impact,  when  strong 
currents  were  used,  would  be  so  destructive  as  speedily 
to  fuse  the  target.  The  anode,  therefore,  was  placed 
only  approximately  at  the  cathode  focus,  with  the 
result  that  the  photographic  definition  obtained  with 
different  tubes  varied  considerably  according  to  the 
position  of  the  anode  in  relation  to  the  cathode  beam. 
The  series  of  pinhole  photographs  (Fig.  3,  a,  h,  c,  d), 
taken  many  years  ago  by  means  of  a  special  arrange- 
ment devised  by  the  author,  are  of  interest  in  this 
connection,  and  a  note  upon  their  meaning  and  method 
of  production  will  be  found  below  the  illustrations. 

The  Cathode  Focus. — In  view  of  the  resulting 
difference  in  photographic  definition,  it  became  a 
matter  of  extreme  importance,  when  selecting  a  tube, 
to  discover  the  exact  relation  of  the  anode  to  the 
cathode  focus.  Some  years  ago  a  method  enabling 
one  to  detect  immediately  which  was  the  best  focussed 
of  a  batch  of  tubes  was  devised  by  the  author.  This 
method  consists  of  placing  a  very  fine  wire  cross  close 
to  the  tube,  one  of  the  wires  being  parallel  to  the 
plane  of  the  anode  or  target  of  the  tube,  and  slightly 
in  advance  of  it  as  in  Fig.  4.  The  tube  is  then 
excited,  and  the  observer,  taking  a  screen,  views  this 
shadow  of  the  cross  from  a  distance  of  10  or  12  inches. 
If  the  X  rays  come  from  a  fine  point  on  the  anode, 
lie  will  be  able  to  see  the  shadow  of  the  cross  with  the 


4       LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

upright  and  horizontal  wires  fairly  equal  in  sharpness; 
but  if  it  should  happen  that  a  large  surface  instead  of 
a  point  is  producing  the  rays,  then,  although  the  wire, 
which  lies  in  the  plane  of  the  anode  will  be  seen  with 
great  clearness,  the  horizontal  wire  will  be  blurred  out 
into  a  ribbon,  or  possibly  rendered  almost  invisible 

(Fig.  5)- 

The  explanation  of  this  phenomenon  is  quite  simple. 
A  line  is  visible  by  reason  of  the  sharpness  of  its 
margins,  and  with  a  shadow  caused  by  a  large  surface 
viewed  end  on,  so  to  speak,  the  wire  which  is  parallel 
to  the  plane  of  the  anode  will  have  the  overlapping 
shadows  from  the  extreme  points,  top  and  bottom, 
of  the  surface  producing  the  shadow  superimposed  in 
the  direction  of  its  length.  On  the  other  hand,  the 
wire  at  right  angles  to  the  plane  of  the  anode  will 
have  its  shadow  produced  also  at  right  angles  to  its 
length,  and  therefore,  under  the  conditions  already 
stated,  will  be  blurred  out  into  the  pattern  of  the 
ribbon.  By  taking  care  always  to  place  the  cross 
at  the  same  distance  from  the  anode  in  the  position 
indicated,  and  making  the  screen  inspection  at  the 
same  distance  from  the  wires,  the  shadow  thus  yielded 
should  enable  one  very  quickly  to  select  the  tube 
having  the  finest  focus. 

Another  method  to  the  same  end,  with  a  result 
perhaps  not  quite  so  obvious,  is  to  replace  the  cross 
wire  with  a  plate  of  lead  in  which  a  very  fine  pinhole 
aperture  has  been  made  with  a  needle.  If  this  pin- 
hole occupies  the  middle  position  between  the  anode 
and  the  screen  (or  a  photographic  plate  protected  in 
its  envelope  in  the  usual  way)^  one  will  be  able  to  obtain 
a  pinhole  image  the  actual  size  of  the  X-ray  producing 
surface   on   the   anode.     The   annexed  figures   show. 


PLATE  III. 


Fig.  4. — Stereoscopic  View   of  X-Ray  Tube   with  Wire  Cross  in 

Position. 


Fig.  5. 

The  wire  parallel  to  the  target  of  the  tube  is  shown  fairly  sharp.     The  other  wire  is 
scarcely  visible,  owing  to  the  diffusion  of  the  shadow. 

[To  face  p.  4. 


PLATE  IV. 


Fig.  6. — Pinhole  Photograph  of  Spot  on 
Target  where  the  X  Rays  originate 
—  Front  View. 


Fig.  7. — End-on  View  of  X-Ray  Producing 
Surface  on  Anode  or  Target  of  a 
Tube. 


[To  face  p.  4 


THE  X-RAY  TUBE  5 

in  the  one  case  (Fig.  6),  the  view  of  the  anode  taken 
directly  from  the  front,  and  in  the  other  (Fig.  7),  the 
vertical  longitudinal  section  or  side  or  profile  view 
of  the  anode.  This  method  furnishes  a  very  exact 
means  of  measuring  the  size  of  the  area  from  which 
X  rays  are  generated  in  any  given  tube.  Many  years 
ago  the  author  constructed  a  tube  having  a  small 
piece  of  osmium  as  a  target  at  the  exact  focus,  and 
this,  being  very  infusible,  gave  splendid  results  and 
resisted  puncture  from  very  strong  currents,  but,  for 
some  unknown  reason,  the  difficulty  of  maintaining  a 
steady  vacuum  proved  insuperable.  In  modern  tubes 
fitted  with  tungsten  targets  this  difficulty  does  not 
seem  to  arise. 

So  much,  then,  for  what  is  meant  by  the  fine  focus 
of  a  tube.  The  production  of  "soft"  and  "hard" 
X  rays — i.e.,  of  low  and  of  high  penetrating  power 
respectively— is  fully  discussed  in  most  of  the  text- 
books, and  need  only  be  mentioned  in  passing.  The 
author  has  ahvays  adhered  to  the  plan  of  having  an 
adjustable  alternative  spark-gap  on  the  terminals  of 
his  coil  to  test  the  hardness  of  the  tube.  On  each 
terminal  there  is  fixed  an  aluminium  ball,  i  cm.  in 
diameter,  which  is  the  arrangement  he  saw  employed 
by  Professor  Rontgen  himself  when  visiting  him  at 
Wiirzburg,  in  Bavaria,  in  1896,  the  year  after  his 
discovery  of  X  rays. 

The  Coolidge  Tube. — A  considerable  departure  from 
standard  X-ray  tube  construction  has  lately  been 
forthcoming  in  the  shape  of  the  new  tube  invented  by 
Mr.  W.  D.  Coolidge,  of  Schenectady,  U.S.A.,  which 
promises  to  be  of  great  utility.  It  possesses  two  good 
recommendations:  in  the  first  place,  the  tube  itself 
acts   as   an   electric   valve,    preventing   any   reversed 


6       LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

current  from  passing  through  it;  and,  in  the  second 
place,  the  quahty  or  penetrative  power  of  the  rays 
can  be  controlled  immediately  at  will  by  an  easily 
adjusted  resistance.  In  the  ordinary  tube  the  cathode 
rays  are  produced  by  the  high-voltage  current  direct 
from  the  induction  coil  or  other  transformer;  in  the 
Coolidge  tube,  on  the  other  hand,  the  cathode  consists 
of  a  fine  coil  of  tungsten  wire,  which  is  raised  to  a  vary- 
ing degree  of  heat,  and  gives  off  electrons  in  a  volume 
proportionate  to  the  amount  of  incandescence  induced 
within  it.  These  electrons,  on  being  set  free,  become 
the  carriers  of  the  ordinary  electrical  impulse  from  the 
induction  coil.  Very  heavy  currents  can  be  passed 
through  this  tube,  and  an  intense  X-ray  output  is 
the  result.  It  is  obvious  that  the  battery  which 
heats  the  little  coil  constituting  the  cathode  must 
be  insulated  when  this  tube  is  worked,  as  it  is  directly 
connected  with  the  negative  terminal  of  the  induction 
coil.  For  therapeutic  purposes,  the  control  of  the 
quality  of  the  X  rays  seems  to  be  a  specially  useful 
feature,  and  the  constancy  of  the  tube  makes  it  still 
more  likely  to  be  of  service  in  treatment.  It  is 
very  important  to  have  a  resistance  with  a  fine 
adjustment  for  the  battery  current  through  the 
tungsten  cathode,  and  it  is  also  advisable  to  have 
an  amperemeter  with  a  very  open  scale,  so  as  to  admit 
of  fine  variations  in  the  amount  of  current  passing 
through  the  small  tungsten  coil  of  wire.  The  current 
required  to  heat  this  coil  seems  to  vary  from  3|-  to 
5  amperes. 


CHAPTER  II 

SECONDARY    RAYS    AND    X-RAY    PROTECTIOX 

Secondary  Rays  from  the  Glass. — In  addition  to 
the  characteristic  beam  issuing  from  the  tube,  other 
X  rays  are  generated  of  which  it  is  very  important 
that  the  worker  should  be  cognizant.  In  the  present- 
day  X-ray  tube  the  area  of  the  glass  bulb  is  very  large, 
and  it  is  apt  to  be  forgotten,  even  by  those  who  have 
paid  great  attention  to  the  physical  side  of  the  subject, 
that  parts  of  this  large  glass  surface  are  giving  off 
radiation  in  considerable  quantities.  These  rays  from 
the  glass  of  the  tube  are  not  only  capable  of  partially 
fogging  the  X-ray  image  proper,  but  also,  in  the 
author's  belief,  they  may  cause  serious  burning  and 
damage  to  the  tissues  of  the  worker,  unless  he  has  been 
forearmed  against  a  danger  so  easily  overlooked. 

An  experiment  which  anyone  can  perform  for 
himself  will  demonstrate  the  existence  of  the  secondary 
or  indirect  rays  coming  from  the  fluorescent  green 
glass  of  the  X-ray  tube.  If  a  piece  cut  off  a  solid 
lead  rod,  about  i  inch  in  thickness,  be  suspended  close 
to  the  glass  of  the  X-ray  tube,  directly  in  front  of  the 
anode  (Fig.  8),  and  the  tube  be  excited,  a  screen  held 
at  some  distance  away  will  have  a  shadow  of  the  lead 
cast  upon  it,  for  lead  to  this  amount  will  allow  no 
X  rays  of  any  sort  or  kind  to  pass  through.  Never- 
theless, actually  within  the  shadow  cast  by  the  lead, 
the  screen  will  not  be  entirely  in  darkness,   and  if 

7 


8       LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

a  piece  of  netting  be  held  slightly  in  front  of  a  photo- 
graphic plate,  in  a  line  with  the  lead  cylinder,  but 
separated  from  it  by  a  short  distance,  a  distinct  shadow 
of  the  mesh  will  be  recorded  upon  the  plate  within  the 
eclipsed  area  (Fig.  9).  The  intervention  of  the  lead 
cylinder  in  the  path  of  the  direct  beam  of  the  primary 
rays  from  the  anode  is  thus  shown  not  to  cancel  the 
X-ray  photographic  effect.  The  effect  on  the  plate 
is  the  result  of  the  action  of  those  rays  which  come 
from  the  glass  of  the  tube  at  such  an  angle  as  to  escape 
the  mass  of  lead. 

In  order  to  demonstrate  that  this  phenomenor^  is 
actually  due  to  the  rays  from  the  glass,  a  single  strip 
of  lead,  very  thick  and  solid,  and  curved  so  as  to 
keep  in  contact  with  the  glass  surface  of  the  tube, 
may  be  placed  across  the  tube  opposite  the  anode  so 
as  to  divide  the  fluorescing  glass  surface  into  halves. 
The  arrangement  is  shown  in  Fig.  10.  If,  then,  a 
thin  piece  of  metal,  such  as  a  knitting-needle,  be 
placed  in  front  of  the  photographic  plate,  within  the 
shadow  of  the  lead  strip,  it  will  be  found  that  a  double 
image  of  this  metal  is  obtained  when  the  photograph 
is  developed  (Fig.  11).  The  reason  for  this  double 
image  is  that,  the  glass  having  been  divided  by  means 
of  the  lead  strip,  each  half  of  the  glass,  by  virtue  of 
the  secondary  rays  issuing  from  it,  produces  its  separate 
image.  The  phenomenon  is  demonstrated  even  more 
strikingly  if,  instead  of  the  single  strip  of  lead,  a  cross 
of  lead  be  placed  in  contact  with  the  glass  surface, 
the  intersection  being  opposite  the  anode.  On  suspend- 
ing a  small  metallic  object  slightly  in  front  of  the  photo- 
graphic plate,  within  the  shadow  of  the  centre  of  the 
cross,  there  will  be  revealed  on  development  of  the 
plate    four   small   images    of     this    object    (Fig.    12), 


PLATE  V. 


Fig.  8. — A  Mass  of  Lead  suspended  Outside  the  Tube  in  Front 
OF  THE  Target,  to  demonstrate  Existence  of  Secondary  Rays 
FROM  the  Glass. 


Fig.  g. — Sharp  Shadow  of  Net  produced  by  Direct  X  Rays  ; 
Blurred  Shadow  produced  by  Secondary  Rays  from  Glass. 

[To  face  p.  8. 


PLATE  VI. 


Fig.  io. — Fluorescing  Glass  Surface  of  Tube  bisected  by  Strip 
OF  Lead,  with  Knitting-Needle  in  Front  in  Position  for 
being  Photographed. 


s'-''^/-^Xf/%' 


Pig.  II. — Double  Image  of  Knitting-Needle  obtained  with 
Tube-Surface  bisected. 

[  To  face  p.  8. 


SECONDARY  RAYS  AND  X-RAY  PROTECTION  9 

showing  that  each  quadrant  of  the  bare  green 
fluorescing  glass  of  the  bulb  has  produced  its  own 
picture.  It  follows  from  all  this  that,  in  order  to  have 
the  maximum  value,  any  diaphragms  which  are  used 
should  be  placed  in  close  contact  with  the  glass  of 
the  tube,  or,  alternatively,  a  tubular  form  may  be 
employed,  the  screen,  of  course,  being  of  lead.  The 
difference  in  definition  obtainable  in  such  a  test 
subject  as  the  mesh  of  a  piece  of  netting  is  discernible 


Fig.  15. 

on  a  comparison  of  Figs.  13  and  14,  the  first  having 
been  taken  with  a  tubular  stop,  and  the  second 
without. 

Nature  of  the  Secondary  Rays. — Without  entering 
upon  the  speculations  which  open  out  as  a  result  of 
these  proofs  of  the  existence  of  secondary  rays  from 
the  glass,  it  is  interesting  to  note  in  passing  that  the 
secondary  X-ray  beam  produced  at  the  glass  surface 
is  probably  complex  in  its  constitution  (Fig.  15). 
Thus  it  includes,  in  the  first  place,  the  secondary 
rays  proper,  the  origin  of  which  is  due  to  the  impact 
of  the  reflected  cathode  rays  from  the  anode,  these 


10     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

latter  being  what  Professor  Silvanus  Thompson  sug- 
gests should  be  called  the  paracathodic  rays;  and,  in 
the  second  place,  secondary  X  rays  are  probably 
produced  also  by  the  passage  of  the  primary  X  rays 
through  the  glass.  These  secondary  rays  from  the 
glass  are  much  more  richly  produced  in  a  ''hard" 
tube,  and  some  comparative  measurements  made  by 
means  of  the  electroscope  showed  that  with  a  ''  hard  " 
tube  emitting  very  penetrating  rays,  if  the  action  of 
the  primary  rays  was  taken  as  one,  that  of  the  second- 
ary rays  might  be  taken  as  one-half;  whereas  with 
a  "  soft  "  tube,  giving  rays  of  a  low  order  of  pene- 
trability, the  primary  rays  again  being  taken  as  one, 
the  secondary  rays  would  be  one-seventh.  Enough 
has  been  said  to  show  that  these  secondary  rays  are 
of  great  importance,  and  certainly  worthy  of  the 
attention  of  those  who  command  the  resources  of  a 
physical  laboratory.  Their  further  study  may  throw 
light  upon  many  obscure  problems  in  X-ray  practice, 
and  it  would  be  at  least  interesting  to  employ  a 
tube  in  which  these  secondary  rays  alone  could  be 
employed  for  experimental  purposes,  with  a  view  to 
their  use  in  therapeutics  should  this  seem  to  be 
advantageous. 

Protective  Devices. — The  question  of  protection 
follows  naturally  upon  the  foregoing,  seeing  that  the 
secondary  or  indirect  rays  given  off  from  the  glass 
may  be,  if  not  the  primary  factor,  certainly  largely 
contributory  to  the  superficial  skin  burns  found 
among  X-ray  operators.  It  is  worthy  of  note  in  this 
connection  that,  with  a  tube  so  high  or  ''hard"  as 
to  give  no  fluorescence  on  the  screen,  Freund  of 
Vienna  found  that  the  radiant  effect  was  such  as  to 
cause  the  epilation  of  the  exposed  part,  and  also  that. 


PLATE  VII. 


Fig.  12. — Four  Images  of  a  Metallic  Object  seen  within  the 
Intersection  of  a  Cross  of  Lead  which  had  been  placed 
IN  Front  of  the  Tube. 


[To  face  p.  lo. 


PLATE  VIII. 


Fig,   13. — X-Ray  Image  of  Netting,  the  Rays  coming 

THROUGH  A  TuBULAR  StOP. 


Fig.   14. — X-Ray  Image  of  Netting,  the   Rays  coming  from 
THE  Naked  Tube. 


[To  face  p.  10. 


SECONDARY  RAYS  AND  X-RAY  PROTECTION        ii 

with  a  tube  having  the  current  passed  in  the  reverse 
direction,  so  as  to  produce  only  ver}^  weak  primary 
rays,  similarly  radical  results  were  obtained.  The 
physiological  action  of  these  secondary  rays  is  proved 
beyond  doubt,  and  is  certainly  considerable  in  view 
of  their  ready  absorption  by  the  skin.  Those  X-raj^ 
workers  who  have  suffered  from  dermatitis  on  the 
hands  have  found  that  the  part  of  the  skin  covered 
by  the  coat  cuff  invariably  has  escaped  the  trouble. 
Seeing  that  the  cloth  offers  no  obstruction  to  the 
primary  rays,  it  seems  evident  that  the  secondary 
rays  have  a  great  deal  to  do  with  causing  the  lesions. 

It   is   well   understood   by   this    time   that   those 
engaged  in  X-ray  work  must  employ  adequate  means 
of  protection,  although  it  may  be  doubted  whether, 
in  view  of  the  large  numbers  of  X-ray  outfits  which 
are  now  being  sent  forth,  and  placed  in  the  control 
of   operators   whose   experience  has   necessarih^  been 
brief,  and  who  have  to  work  under  conditions  of  great 
pressure,  the  rigid  necessity  of  abundant  protection 
is  fully  appreciated.     The  lower  the  atomic  weight  of 
a  substance,  the  more  easily  is  it  penetrated  by  X  rays, 
and  therefore  lead,  being  one  of  the  heaviest  and  also 
one  of  the  most  economical  of  metals,  is  most  service- 
able  for   protective   purposes.     Many   years   ago   the 
author  buried  an  X-ray  tube  in  a  large  box  filled  with 
red  lead,  for  it  so  happens  that  the  oxides  of  metals 
which  themselves  are  good  conductors  are  excellent 
insulators.     Wires  were  attached  to  this  buried  tube 
in  the  usual  way,  and  it  was  excited  in  a  completely 
dark  room.     A  fluorescent  screen  was  moved  about 
around  the  box  in  all  directions,  and  not  the  slightest 
evidence   of   the   passage   of   any   X   rays   was   forth- 
coming.    Then,  from  a  point  approximately  opposite 


12     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

the  anode,  the  red  lead  was  gradually  scooped  aside 
until  a  faint  ghmmer  of  fluorescence  revealed  itself 
on  the  screen.  In  the  case  of  the  tube  with  which  the 
experiment  was  made,  it  was  found  that  a  thickness 
of  red  lead,  equal  to  at  least  half  an  inch,  was  required 
to  stop  the  rays  from  passing  through.  As  the  red 
lead  was  a  fine  and  heavy  powder,  most  unsuitable 
for  practicable  use,  a  wooden  box,  large  enough  to 
contain  the  tube,  was  coated  on  its  inner  side  with  a 
putty  made  up  of  red  lead  and  the  white  lead  of  the 
shops.  This  was  put  on  in  a  thick  layer  all  round  the 
box,  and  a  hole  was  cut  in  the  lid,  against  which  the 
anterior  part  of  the  tube  was  secured  by  elastic  bands. 
This  white  and  red  lead  hardened  into  a  solid  mass, 
which  kept  radiation  under  control,  cutting  off  all  the 
rays  save  those  which  were  allowed  to  come  through 
the  aperture  in  the  lid  of  the  box.  A  box  of  this 
kind,  naturally,  was  heavy,  but  there  is  no  way  of 
obviating  this  disadvantage  in  view  of  the  fact  that 
it  is  only  heavy  substances  which  suffice  to  cut  off 
the  unwanted  rays. 

Screens,  Gloves,  etc. — x\t  the  present  time  some 
such  protection  is  supplied  by  the  tube-makers.  It 
consists  of  a  combination  of  lead  and  rubber,  which, 
if  of  sufficient  thickness,  acts  as  quite  a  good  means 
of  protection.  Another  plan  which  is  ver}/  serviceable 
is  to  surround  the  X-ray  table  with  screens  of  lead 
of  considerable  thickness,  such  as  is  used  for  roofing 
houses,  this  lead  being  sandwiched  between  sheets  of 
wood.  The  worker  can  stand  behind  these  screens, 
should  it  be  necessary  to  use  the  tube  in  an  insufficiently 
protected  condition.  The  screens  can  be  fixed  on  a 
narrow  stand,  with  "domes  of  silence"  or  castors,, 
which  enable  them  to  be  moved  to  any  required  posi- 


SECONDARY  RAYS  AND  X-RAY  PROTECTION        13 

tion.  Gloves  made  of  dense  material  are  provided 
for  the  hands,  which  must  at  times  come  within  the 
direct  beam,  and  another  measure  of  protection  is  to 
glaze  the  fluorescent  screen.  This  should  be  done 
with  very  dense  lead  glass,  which  allows  the  useful 
visible  rays  to  pass  through  unimpeded,  but  cuts  off 
a  considerable  amount  of  the  dangerous  radiation. 
Should  prolonged  screen  examination  be  necessary 
for  any  reason,  the  author  would  suggest  having  a 
fine  plane  glass  mirror  on  a  stand  so  adjusted  as  to 
enable  the  worker  to  watch  the  reflection  of  the 
fluorescent  screen  while  he  himself  is  standing,  effec- 
tively protected,  behind  one  of  the  big  lead  barriers 
just  described. 

By  this  method  of  reflection,  also,  an  ordinary 
photographic  camera  can  be  made  to  record  the  image 
produced  by  the  fluorescent  screen.  As  the  rays  are 
of  a  yellowish-green  tint  on  the .  best  screens  (those 
of  barium  platinocyanide) ,  it  is  advisable  to  use 
panchromatic  plates  for  the  purpose;  a  screen  of 
tungstate  of  lime  or  of  barium  potassium  cyanide  will 
fluoresce  blue,  and  be  photographically  more  speedy. 
In  this  way  a  15  by  12  inch  screen  could  be  photo- 
graphed down  to  lantern-slide  size  direct,  but  the 
exposure,  judging  from  some  brief  experiments,  would 
be  too  lengthy  to  make  the  method  of  much  practical 
value. 


CHAPTER  III 

X-RAY    STEREOSCOPY 

The  Misleading  Single  Picture. — It  has  been  stated 
already  that  X  rays  travel  in  straight  lines  from  their 
point  of  origin  on  the  anode  to  their  destination,  be  it 
photographic  plate  or  fluorescent  screen.  An  X-ray 
photograph,  therefore,  is  simply  a  shadowgraph  of  an 
interposed  object,  differing  from  the  shadowgraph 
produced  by  light  in  that  it  reveals  the  interior  of 
the  object  as  well  as  its  outline.  From  a  single  X-ray 
silhouette  the  relative  position  of  the  objects  giving 
rise  to  the  shadows  of  varying  density  can  only  be 
guessed,  and  very  erroneous  impressions  may  result. 
An  example  of  the  range  of  error  which  is  possible 
is  given  in  the  annexed  illustration  (Fig.  i6),  in  which 
the  shadow  cast  by  a  pair  of  scissors  is  shown  to  be 
capable  of  more  than  one  interpretation.  On  looking 
at  the  right-hand  picture,  the  nature  of  the  object 
could  not  be  understood,  but  the  stereoscopic  view 
shows  immediately  the  fact  that  it  is  a  pair  of  scissors, 
and  its  position. 

The  application  of  the  stereoscopic  method  to 
X-ray  work  was  recognized  by  the  author  as  a  vital 
necessity  very  shortly  after  the  discovery  of  X  rays 
was   announced. 1    Those  who   are   interested  in   the 

1  J.  Mackenzie  Davidson:  "Remarks  on  the  Value  of  Stereo- 
scopic Photography  and  Skiagraphy,"  British  Medical  Journal, 
December  3,  1898. 

14 


X-RAY  STEREOSCOPY  15 

principles  underlying  stereoscopy  (which,  briefly  stated, 
is  the  direct  perception  of  the  relative  distances  of 
near  objects)  may  be  referred  to  the  work  of  Wheat- 
stone,  who  was  the  first  to  put  forward  the  hypothesis 
that  the  perception  of  depth  was  due  to  the  difference 
between  the  two  retinal  images.^  Another  and  rather 
later  pioneer  is  Brewster,-  and  the  writings  of  both 
these  workers,  although  dating  back  for  considerably 
more  than  half  a  century,  deserve  the  most  careful 
study  if  the  stereoscopic  theory  is  to  be  thoroughly 
grasped.  A  more  modern  exposition  of  the  principles 
of  binocular  vision  is  that  of  le  Conte.^ 

Preliminary  Arrangements. — In  order  to  produce 
X-ray  photographs  stereoscopically,  it  is  essential 
either  to  have  the  X-ray  tube  held  in  a  tube-holder 
which  admits  of  displacement  in  a  definite  direction, 
or,  what  is  more  usual,  to  place  the  tube  in  some  form 
of  protective  box  which  can  be  made  to  slide  from  one 
position  to  another.  It  is  much  more  convenient  to 
work  with  a  tube  beneath  the  couch  upon  which  the 
patient  is  lying  than  to  work  with  a  tube  placed  above 
the  couch,  but  some  workers  prefer  the  latter  arrange- 
ment. Most  couches  are  so  constructed  that  the  tube 
can  slide  backwards  and  forwards  from  head  to  foot 
parallel  to  the  length  of  the  couch,  and  also  crosswise 
from  side  to  side  at  right  angles  to  the  length.  With 
these  two  movements,  it  is  obvious  that  the  tube  can 
be  brought  to  any  desired  position  in  relation  to  the 

^  The  Scientific  Papers  of  Sir  C.  Wheaistone.  Reprinted  from 
the  Philosophical  Transactions  of  1S3S.  Pubhshed  by  the  Ph\'sical 
Society  of  London,  1879. 

^  Stereoscopy  :  its  History,  Theory,  and  Construction.  By  Sir 
David  Brewster.     (John  Murray,  1856.) 

^  Sight.  By  Joseph  le  Conte,  LL.D.  International  Scientific 
Series,  vol.  xxxiii.     (Keean  Paul,  Trench,  and  Co.,  1S95.) 


i6     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

couch  above.  The  arrangements  by  which  these 
movements  are  effected  naturally  vary  considerabty 
in  detail  as  between  one  couch  and  another,  and  in  a 
later  chapter  a  very  simple  and  portable  construction 
will  be  described.  In  the  meantime  it  is  sufficient 
to  say  that,  given  this  arrangement  of  a  mobile  tube- 
box,  some  means  must  be  furnished  for  determining 
the  position  of  the  vertical  ray  coming  from  the  anode 
of  the  tube.  Once  the  position  of  that  vertical  ray 
is  ascertained,  it  is  definitely  recorded  by  means  of  a 
plumb-bob  attached  to  an  adjustable  horizontal  arm 
above  the  couch,  this  arm  jutting  from  a  vertical 
support  which  is  fastened  to  the  tube-box  below,  and 
moves  with  it. 

The  Vertical  Ray. — The  position  of  this  vertical 
ray  can  be  determined  by  any  one  of  several  simple 
ways.  One  of  the  most  convenient  is  to  use  a  small 
celluloid  box  in  which,  immediately  beneath  the  lid 
or  top,  two  fine  needles  or  wires  are  fixed  at  right 
angles  to  each  other.  From  the  intersection  of  these 
wires  is  suspended  into  the  interior  of  the  box  a  small 
metal  plumb-bob.  In  order  to  make  the  plumb-bob 
cease  its  oscillations  quickly,  it  may  be  immersed  in 
a  thickish  fluid,  such  as  thick  paraffin.  Instead  of  the 
ordinary  lid,  a  small  fluorescent  screen  is  used  to  cover 
the  box,  and  is  thus  in  immediate  contact  with  the 
cross  wires  below.  When  this  arrangement  is  placed 
upon  the  couch,  and  the  tube  is  excited  in  a  darkened 
room,  the  shadow  of  the  small  plumb-bob  and  of  the 
cross  wires  will  be  visible  on  the  screen,  and  the  box 
can  be  readily  moved  to  such  a  position  that  the 
shadow  of  the  plumb-bob  is  directly  below  the  point 
where  the  wires  intersect.  It  is  obvious  that  the 
anode   from   whence   come   the   rays   producing   this 


PLATE   IX. 


Fig.  1 6. — The  Shadow  cast  by  a  Pair  of  Scissors,  showing 
HOW  misleading  a  Non-Stereoscopic  Picture  may  be. 


Fig.  17. — The  Wheatstone  Stereoscope. 


To  facep.  16. 


X-RAY  STEREOSCOPY  17 

shadow  must  be  vertically  below  the  cross  wires, 
and  it  is  only  necessary  then  to  adjust  the  arm  attached 
to  the  perpendicular  support  so  that  the  plumb-bob 
mentioned  in  the  preceding  paragraph  as  being  sus- 
pended from  this  arm  rests  upon  the  point  of  inter- 
section of  these  cross  wires.  Once  fixed  in  this 
position,  it  follows  that  this  indicator  arrangement, 
which  moves  with  the  tube,  will  always  denote  the 
point  vertically  beneath  which  the  anode  is  situated, 
no  matter  how  much  the  tube  may  be  moved  up  and 
down  or  from  side  to  side  of  the  couch.  This  plumb- 
bob  arrangement,  or  some  similar  device,  must  alwa}'S 
be  employed  if  stereoscopic  photographs  are  to  be 
taken  or  an}-  method  of  precise  localization  adopted. 

The  Two  Exposures. — This  preliminary  condition 
having  been  fulfilled,  the  following  simple  method  will 
at  once  enable  a  worker  to  produce  two  stereoscopic 
negatives.  The  subject  to  be  photographed  is  placed 
upon  the  couch,  and  the  point  of  view  from  which  it 
is  desired  to  take  the  photograph  is  decided  upon. 
The  tube-box  beneath  the  couch  is  moved  about, 
the  indicator  mo\dng  with  it,  until  the  plumb-bob 
suspended  from  the  pointer  rests  upon  the  selected 
position.  A  photographic  plate,  contained  in  the 
usual  carrier  or  paper  envelope,  is  placed  upon  the 
subject  in  such  a  manner  that  two  of  its  edges  are 
parallel  with  the  long  axis  of  the  couch.  Its  position, 
for  reference  purposes  in  view  of  the  second  exposure, 
is  recorded  by  means  of  blue  pencil  simply  run  along 
two  adjacent  sides.  The  necessary  exposure  is  then 
given,  after  which  another  plate  is  placed  in  exactly 
the  position  occupied  by  the  first.  The  tube  is  dis- 
placed by  6  cm.  (the  interocular  distance)  to  one 
side — the  right  or  left — along  either  axis  of  the  couch. 


i8     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

The  nature  of  the  subject  will  determine  which  move- 
ment out  of  the  possible  four  shall  be  taken.  The 
second  exposure  having  been  made,  the  two  plates 
are  developed,  and  the  results  viewed  stereoscopically. 
To  persons  possessed  of  binocular  vision,  these  two 
photographs,  when  viewed  in  a  Wheatstone  stereoscope, 
give  an  impression  of  striking  relief.  The  image 
appears  to  have  rotundity,  and  to  be  seen  in  three 
dimensions — namely,  length,  breadth,  and  thickness — 
instead  of  in  the  first  two  only,  as  with  the  single 
picture. 

The  Wheatstone  Stereoscope. — The  one  essential 
in  all  stereoscopic  procedures  is  that  each  eye  shall 
see  only  its  own  image.  The  Wheatstone  stereoscope 
(Fig.  17),  already  alluded  to,  is  one  of  the  simplest 
of  viewing  methods,  consisting  merely  of  two  mirrors 
placed  at  right  angles  to  each  other,  the  apex  being 
towards  the  observer.  When,  therefore,  the  observer 
approaches  the  line  at  which  the  two  mirrors  join,  the 
right  eye  can  only  see  the  reflection  of  the  photograph 
placed  opposite  the  mirror  to  the  right,  and  the  left 
eye  the  reflection  in  the  other  mirror  (Fig.  18).  The 
two  negatives  are  placed  in  the  holder  at  equal  dis- 
tances from  the  centre  of  each  mirror,  and  are  illumin- 
ated by  some  suitable  arrangement.  If  prints  from 
the  negatives  are  viewed,  no  special  illumination  is 
necessary,  as  these  can  be  seen  by  ordinary  reflected 
light.  All  that  the  observer  has  to  do  is  to  move 
the  support  of  the  mirrors  backwards  and  forwards 
until  he  gets  the  single  image  in  stereoscopic  relief. 
The  beginner  will  find  it  convenient  to  pull  the  mirror 
towards  him  until  he  sees  the  two  photographs  side 
by  side  and  overlapping;  then,  by  gradually  pushing 
the  mirrors  away,  keeping  the  middle  line  of  his  fore- 


PLATE  X. 


Fig.   1 8. — Method  of  Viewing  with  the  Wheatstone 
Stereoscope. 


Fig.   19. — Method  of  Viewing  with  the  Brewster  or 
Lenticular  Stereoscope. 


[To  face  p.  18. 


X-RAY  STEREOSCOPY  19 

head  close  to  the  apex,  he  will  find  that  the  images 
gradually  approach  each  other,  and  finally  fuse  into 
one,  whereupon  this  solid  stereoscopic  effect  is  immedi- 
ately realized.  After  a  short  time  the  solidity  of  the 
image  seems  to  grow  upon  the  attention  of  the 
observer. 

Another  feature  of  the  stereoscopic  view  which  has 
a  physiological  interest,  and  in  the  case  of  surgical 
work  a  practical  importance,  is  that  by  transposing 
the  photographs  (i.e.,  taking  the  one  on  the  right 
and  placing  it  on  the  left,  and  vice  versa)  the  point 
of  view  becomes  reversed.  Thus,  if  a  hand  be  photo- 
graphed stereoscopically,  and  the  negatives  be  so 
placed  that  the  observer  seems  to  be  looking  on  to 
the  back  of  a  right  hand,  the  transposition  of  the 
two  pictures  in  the  way  indicated  will  make  it  appear 
as  though  he  were  looking  into  the  palm  of  a  left. 
This,  at  first,  may  seem  rather  mysterious,  but  if 
Wheatstone's  paper,  to  which  reference  has  already 
been  made,  be  consulted,  the  explanation  of  the 
phenomenon  will  be  found  to  be  quite  simple. 

Other  Viewing  Methods. — These  two  negatives,  if 
they  have  been  taken  on  large  plates,  can  be  reduced 
photographically  to  the  usual  size  of  two  lantern 
plates,  and  the  stereoscopic  transparency  thus  pro- 
duced may  be  viewed  in  the  more  generally  known 
lenticular  or  Brewster  stereoscope  (Fig.  19).  This  is 
a,  considerable  convenience  in  cases  in  which  a  surgeon, 
while  operating,  desires  to  refresh  his  memory  by 
viewing  the  stereoscopic  photograph  of  the  case.  If 
these  reductions  to  lantern  size  are  made  on  two 
separate  lantern  plates,  it  is  possible  to  show  them 
singly  on  the  screen  for  teaching  purposes,  and  at  the 
same  time,  using  a  little  holder  with  a  ground-glass 


20     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

background,  to  vary  the  stereoscopic  picture  by 
transposition  in  the  manner  already  described.  When 
once  a  good  stereoscopic  X-ray  photograph  has  been 
obtained,  it  becomes  unnecessary  to  point  out  the 
reahstic  beauty  of  the  picture  or  its  enormous  impor- 
tance in  medical  and  surgical  work. 

Stereoscopic      Screen-Images. — Those      who      are 
familiar  with  stereoscopic  X-ray  photographs  do  not 
need  to  be  reminded  of  the  immense  utility  of  any 
method  which  would  render  possible  a  stereoscopic 
image  on  the  fluorescent  screen.     Several  years  ago 
the   author  produced  an  apparatus  having  this  end 
in  view,  and  it  was  shown  at  Charing  Cross  Hospital,, 
and  again  at  a  conversazione  of  the  Royal  Society. 
The   principles   involved   are   quite   simple,    but   the 
mechanical   methods    of   carrying   them   out   can   be 
varied  very  greatly.     The  main  condition  is  to  have 
two  X-ray  tubes  (or  one  specially  constructed  X-ray 
tube  having  two  anodes)  placed  side  by  side,  so  that 
the  line  connecting  the  points  of  X-ray  production 
on  the  anodes  is  horizontal.     The  screen  has  to  be 
placed  behind  the  object  and  in  front  of  the  tubes, 
and  some  mechanical  arrangement  must  be  devised 
whereby   the   tubes   can   be   illuminated   alternately. 
Synchronous   with   this    alternate   illumination   there 
must  be  the  action  of  a  collapsing  or  rotating  shutter, 
so  as  to  insure  that,  when  one  tube  casts  a  shadow  on 
the  screen,  it  shall  be  seen  by  only  one  eye  of  the  ob- 
server; and  when  the  second  tube  is  illuminated,  the 
first  must  be  eclipsed,  so  that  the  shadow  is  visible 
only  to  the  other  eye.     If  this  action  is  repeated  at  a 
rate   of   ten   alternations  per  second,  the   impression 
made  upon  each  eye  becomes  continuous,  owing  to  the 
persistence    of    the   retinal   images.     Thus,   each    eye 


X-RAY  STEREOSCOPY  21 

sees  its  own  image,  and  the  combination  gives  a 
stereoscopic  result.  The  advantage  of  this  method 
is  obvious,  but  there  are  many  mechanical  difficulties 
which  make  the  carrying  of  it  out  and  its  maintenance 
in  proper  working  order  somewhat  problematical. 
These  difficulties  have  prevented  the  method  from 
coming  into  general  use  up  to  the  present  time,  but 
the  author  is  convinced  that,  when  these  have  been 
surmounted,  it  will  prove  eventually  to  be  one  of  the 
most  useful  and  reliable  methods  of  medical  and 
surgical  X-ray  investigation  at  command. 


CHAPTER  IV 

RAPID    X-RAY   LOCALIZATION 

A  New  X-Ray  Couch. — Before  entering  in  detail 
into  the  methods  of  locahzation  recommended  by 
the  author,  it  will  be  convenient  to  describe  a  simple 
and  portable  X-ray  couch  which  he  has  recently 
devised  for  the  purpose  of  facilitating  X-ray  examina- 
tion. The  couch  in  question  (Fig.  20)  consists  essenti- 
ally of  two  ordinary  hinged  trestles  upon  which  can 
be  placed  the  standard  Army  stretcher.  From  one 
of  the  rests  of  the  stretcher  a  couple  of  rails  are  made 
to  connect  with  the  opposite  rest,  and  these  rails  are 
hinged  at  the  points  of  union  with  the  stretcher,  and 
also  in  the  middle,  so  that,  when  the  stretcher  and  the 
tube-box  are  removed,  the  rails  can  be  packed  up 
into  quite  a  small  compass.  On  the  rails  there  is 
placed  a  small  board  which  runs  along  the  whole 
length  of  the  couch,  and  is  moved  and  controlled  by 
an  upright  arrangement  which,  with  a  windlass,  makes 
movement  easy  along  the  rails  placed  lengthwise  and 
from  side  to  side  of  the  couch.  The  tube-box,  which 
is  lined  with  lead  rubber,  is  secured  to  U-shaped  pillars 
by  thumb-screws,  so  that  its  distance  from  the  couch 
can  be  regulated  by  the  simple  movement  up  or  down 
of  these  supports.  From  one  side  of  the  board  which 
supports  the  tube-box  there  projects  a  stout  V-shaped 
upright,  having  a  horizontal  hinged  arm  capable  of 

an   up-and-down    movement.      On   the   end    of    this 

22 


RAPID  X-RAY  LOCALIZATION 


23 


24     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

horizontal  arm  is  a  small  piece  of  wood  with  cross 
wires,  and  by  means  of  a  slot  and  thumb-screw  attach- 
ment this  can  be  adjusted  so  that  the  intersection  of 
the  cross  wires  is  secured  vertically  above  the  anode. 
On  the  top  of  this  vertical  support,  if  it  is  desired, 
another  arm  can  be  secured  by  a  thumb-screw,  and 
can  be  made  to  carry  a  small  plumb-bob. 

The  convenience  of  this  couch  consists  in  its 
portability,  its  lightness,  and  the  virtual  absence  of 
metal  parts,  thereby  obviating  the  danger  of  those 
unpleasant  shocks  which  are  often  administered  when 
metallic  couches  are  used.  Its  wooden  construction 
has  the  further  advantage  of  enabling  it  to  be  pro- 
duced readily,  whereas  all  metal  work,  at  the  moment 
of  writing,  is  handicapped  by  the  necessities  of  the 
war.  If  anything  did  require  repairing,  this  could 
easily  be  done.  The  incorporation  of  the  stretcher 
is  of  value,  not  only  from  the  point  of  view  of  the 
comfort  of  the  wounded,  but  also  from  that  of  the 
rapidity  with  which  cases  may  be  dealt  with. 

Conditions  for  Localization. — Turning  now  to  the 
subject  of  the  localization  of  foreign  bodies,  the  first 
necessary  condition  is  that  the  body  to  be  localized 
shall  be  of  sufficient  atomic  density  to  give  a  shadow 
capable  of  being  differentiated  from  the  shadows  of 
the  tissues  in  which  it  is  embedded.  Splinters  of 
wood,  portions  of  clothing,  and  similar  material 
which  may  be  carried  into  a  wound,  are  not  detectable 
by  X  rays.  Localization  is  virtually  confined,  there- 
fore, to  cases  in  which  the  foreign  body  is  a  particle 
of  metal,  or  a  piece  of  glass  or  rubber  tubing,  more 
especially  vulcanite.  A  great  many  different  methods 
of  localization  have  been  brought  forward,  but  for 
the  time  being  we  will  content   ourselves  with   de- 


RAPID  X-RAY  LOCALIZATION  25 

scribing  the  simplest  of  these  and  the  most  rapid, 
with  a  view  to  existing  circumstances. 

All  methods  of  localization  w^hich  make  any 
pretence  to  precision  must  necessarily  depend,  in  the 
first  place,  upon  ascertaining  the  position  of  the 
vertical  or  normal  ray;  and,  in  the  second  place, 
upon  the  shifting  of  the  shadow  caused  by  the  dis- 
placement of  the  tube  to  a  known  distance.  This 
point  has  already  been  dealt  with  in  a  former  chapter, 
and  it  is  only  repeated  here  in  order  that  the  reader 
may  be  reminded  how  crucial  a  point  it  is.  The 
position  of  this  vertical  ray  having  been  determined 
in  the  manner  described  on  p.  16,  and  the  plumb- 
bob  or  horizontal  arm  of  the  cross  wires  adjusted  to 
it,  the  patient  is  placed  upon  the  couch,  the  cross 
wires  are  so  arranged  as  to  be  almost  in  contact  with 
his  skin,  and  the  tube  is  excited  in  the  dark-room. 
By  means  of  the  screen  placed  over  the  cross  wires, 
it  is  then  possible  to  see  the  relation  which  these 
wires  bear  to  the  position  of  the  foreign  body.  The 
tube  is  moved  about  until  the  foreign  body  casts  its 
shadow  immediately  beneath  the  wires,  and  this 
point  is  marked  on  the  patient's  skin.  What  we  have 
now  ascertained  is  that  the  foreign  body  is  vertically 
below  this  point  marked  on  the  skin  so  long — but 
only  so  long — as  the  patient  maintains  that  particular 
position,  which  must  be  carefully  noted.  All  that 
remains  to  be  done  is  to  ascertain  at  what  depth 
beneath  this  point  the  foreign  body  is  lying. 

Measurement  on  the  Screen. — -While  the  patient 
remains  immobile,  the  tube-box  should  be  adjusted — 
i.e.,  moved  higher  or  lower — so  that  the  anode  is 
exactly  50  cm.  from  the  marked  point  on  the  skin. 
When  this  has  been  done,  a  small  and  very  simple 


26     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

apparatus  (Figs.  21  and  22)  can  be  used  to  give  immedi- 
ately the  depth  of  the  bullet  or  other  metal.  The 
little  instrument  consists  of  a  very  thin  piece  of  wood, 
having  grooves  to  admit  a  sliding  piece,  and  forming 
the  framework  of  a  couple  of  cross  wires  inserted  at 
right  angles  to  each  other.  The  point  of  intersection 
of  these  wires  is  at  the  centre  of  a  circle  aperture, 
about  the  size  of  half  a  crown,  which  is  cut  in 
the  wood.  The  whole  arrangement  should  have  an 
ample  margin  of  lead  rubber  to  protect  the  hands  of 
the  operator.  A  sliding  piece,  having  another  wire 
fixed  across  its  U-shaped  extremity,  is  then  inserted 
into  the  larger  piece  of  wood  in  such  a  manner  that 
the  wire  it  carries  can  be  brought  to  rest  immediately 
below,  and  in  contact  with,  one  of  the  stationary 
intersecting  wires.  This  can  also  be  withdrawn  to  the 
right  of  the  operator,  so  that  there  may  be  a  definite 
space  between  the  stationary  and  the  movable  wire. 
A  little  ivory  scale  is  attached  to  the  projecting  handle 
of  the  slide,  and  on  this  the  extent  of  the  displacement 
is  read  off. 

If,  now,  the  point  where  the  wires  intersect  is 
adjusted  so  as  to  be  exactly  over  the  mark  already 
made  on  the  skin,  one  wire  being  parallel  to  the  long 
axis  of  the  couch,  and  the  other  at  right  angles  to  it, 
and  a  screen  be  placed  over  this  little  apparatus,  the 
screen,  when  illuminated,  will  show — if  the  previous 
adjustments  have  not  been  disturbed — that  the  shadow 
of  the  foreign  body  is  exactly  vertically  below  the 
intersection  of  the  cross  wires.  The  tube-box  is  then 
displaced  by  10  cm.  to  the  left  of  the  observer,  where- 
upon it  will  be  noted  that  the  foreign  body  has  been 
displaced  on  the  screen  to  the  observer's  right,  and 
now  appears  to  be  at  some  distance  from  the  point 


RAPID  X-RAY  LOCALIZATION 


27 


Fig.  21. 


Fig.  22. 


28     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

of  intersection.  The  precise  distance  is  in  direct 
relation  to  the  depth  at  which  the  foreign  body  is 
situated  below  the  skin.  The  observer  now  with- 
draws the  sliding  arrangement  until  the  shadow  of 
the  wire  it  carries  cuts  the  shadow  of  the  foreign  body 
in  exactly  the  same  manner  as  it  did  when  the  axial 
ray  was  producing  the  shadow  in  the  first  instance. 
The  little  scale  on  the  instrument,  to  which  allusion 
has  already  been  made,  will  then  register  the  exact 
depth  of  the  embedded  metal  below  the  marked 
point  on  the  skin.  It  seems  to  the  author  that  if  a 
ready  means  of  adjusting  the  distance  of  the  tube  to 
the  marked  point  on  the  skin  can  be  found,  this  method 
furnishes  one  of  the  very  quickest  means  of  localizing 
a  foreign  body.  Obviously,  it  takes  much  longer  to 
describe  a  method  of  this  kind  than  to  carry  it  out. 

Methods  analogous  to  this,  all  based  on  the 
principle  of  similar  triangles,  have  been  described 
recently  by  Dr.  William  Hampson  and  Captain 
Thurstan  Holland,  and  tables  prepared  and  supplied 
by  them  take  the  place  of  the  direct  reading  scale 
which  has  been  calibrated  for  this  apparatus. 


CHAPTER  V 

THE    CROSS-THREAD    METHOD 

Precise  Localization. — In  the  previous  chapter, 
having  in  mind  the  necessity  for  dealing  quickly  with 
large  numbers  of  cases,  we  discussed  the  most  rapid 
methods  of  screen  localization.  Much  more  has  to 
be  said,  however,  if  the  principles  involved  in  X-ray 
localization  are  to  be  grasped.  The  rapid  methods 
may  suffice  in  conditions  of  emergency,  and  for  the 
more  obvious  cases,  but  the  formulation  of  a  precise 
localization  method  applicable  to  every  condition 
demands  certain  scientific  considerations,  and,  accord- 
ingly, we  shall  even  have  to  go  over  more  elaborately 
some  of  the  ground  already  roughly  covered  in  order 
to  arrive  at  a  complete  understanding  of  the  subject. 

Cognizance  must  be  taken,  in  the  first  place,  of 
certain  elementary  facts  in  geometry.  While  the 
method  of  precision  presently  to  be  described  can  be 
carried  out  purely  by  mechanical  measurements, 
without  any  knowledge  of  mathematical  formula,  it 
is,  nevertheless,  entirely  dependent  upon  geometry; 
and  in  order  to  make  it  intelligible,  it  is  well  to  refresh 
the  memory  as  to  certain  geometrical  propositions. 
We  encounter  a  geometrical  consideration  at  the 
outset,  for  the  shadow  cast  by  an  X-ray  tube  is,  in 
geometrical  language,  a  central  projection,  and  there- 
fore shows  the  object  on  an  enlarged  scale.  This  is 
in  contrast  to  parallel  projection,  which  latter  would 

20 


30     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 


give  a  shadow  of  the  outhne  the  exact  size  of  the 
actual  object.  Fig.  23  ihustrates  what  is  meant  by 
central  and  parallel  projection. 

On  the  question  of  localization  we  have  first  to 
remember  that  if  two  straight  lines  intersecting  each 
other  at  right  angles  are  drawn  upon  a  plane  surface, 
any  point  marked  on  that  surface  may  have  its  position 
defined  absolutely  if  its  perpendicular  distances  from 


Fig.  23. 

the  two  lines  are  stated.  This  method  is  the  familiar 
one  by  which  the  position  of  points  on  temperature 
charts  and  recording  barometric  projections  is  deter- 
mined. The  base  line  is  called  the  abscissa,  or  OX 
co-ordinate,  and  may  be  denoted  by  X]  and  the 
vertical  line  is  called  the  ordinate,  or  OY  co-ordinate, 
and  may  be  denoted  by  Y. 

This,  however,  is  a  method  applicable  to  only 
two  dimensions  on  a  plane  surface,  but  our  world  is 
one  of  three  dimensions — namely,  length,  breadth,  and 
thickness.     Points  in  space  can  have  their  position 


THE  CROSS-THREAD  METHOD 


31 


defined  in  the  same  manner  by  co-ordinates,  providing 
there  are  three  planes  of  reference,  all  at  right  angles 
to  each  other  (Fig.  24).  An  illustration  will  help 
those  unfamiliar  with  geometry  to  understand  this 
statement.  In  the  corner  of  a  room  we  have  an 
instance  of  two  walls  meeting  at  right  angles  to  each 
other,  and  a  floor  which  is  at  right  angles  to  each  of 
the  two  walls.  The  walls  and  the  floor,  therefore, 
furnish  an  example  of  three  planes,  all  at  right  angles 
to  each  other.  Any 
point  in  space  may 
have  its  position  de- 
fined by  measuring  its 
vertical  distance  from 
the  one  wall,  which  we 
may  call  X;  its  verti- 
cal distance  from  the 
other  wall,  which  we 
may  call  Y;  and  then 
its  vertical  distance 
above  the  floor,  which 
we  may  call  Z.  These  distances  are  described  as  the 
co-ordinates  of  the  point  in  question  with  reference 
to  these  three  planes.  Further,  the  position  of  this 
point  with  reference  to  any  other  point  can  be  ascer- 
tained by  measuring  in  a  similar  way  the  three  co- 
ordinates of  the  other  point,  and  making  a  simple 
subtraction. 

Applied  Geometry. — We  will  proceed  now  to  con- 
sider how  this  co-ordinated  geometry  in  three  dimen- 
sions may  be  applied  to  ascertaining  with  extreme 
accuracy  the  exact  position,  and,  moreover,  the  exact 
size,  of  a  foreign  body  in  the  tissues.  If  the  principles 
of  the  method  are  thoroughly  understood,  the  arrange- 


FiG.  24. 


32     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

ments  for  their  application  can  be  varied  in  a  number 
of  ways. 

It  is  necessary,  in  the  first  place,  to  have  two 
intersecting  wires  stretched  on  a  frame  at  right  angles 
to  each  other.  The  point  on  the  anode  from  which 
X  rays  take  their  origin  must  be  placed,  by  an  adjust- 
ment of  the  tube-holder,  in  a  position  vertically  above 
or  vertically  below  the  point  of  intersection  of  these 
wires.  The  exact  distance  of  this  point  on  the  anode 
must  be  ascertained,  and  will  be  expressed  most 
conveniently  in  the  metrical  system.  It  is  necessary, 
also,  to  have  some  suitable  arrangement  in  the  tube- 
holder  for  allowing  the  tube  to  be  moved  parallel 
to  one  of  these  intersecting  wires. 

These  arrangements  being  carried  out,  the  part 
of  the  patient  to  be  examined  is  placed  upon  the  cross 
wires,  and  the  photographic  plate  below  the  wires 
(or  above  them,  as  the  case  may  be).  The  author 
usually  arranges  that  the  anode  of  the  tube  be  moved 
parallel  to  one  of  the  wires  a  distance  of  3  cm.  to 
one  side  (say  the  right)  of  the  vertical  wire.  The 
first  photograph  is  then  taken.  The  exposed  plate 
having  been  removed  and  marked,  another  is  put  in 
its  place,  care  being  taken  not  to  move  the  patient 
during  this  exchange.  This  is  most  conveniently 
done  if  the  cross  wires  are  arranged  over  a  frame  of 
stretched  parchment  such  as  is  used  for  making  drums ; 
or,  if  the  frame  is  placed  above  the  patient,  and  the 
tube  below  the  couch,  then  the  plate  can  simply  be 
laid  on  the  frame,  and  changed  without  disturbing 
either  the  position  of  the  patient  or  the  wires.  Before 
the  second  photograph  is  taken,  the  tube  is  displaced 
6  cm.  from  the  position  it  occupied  during  the  first 
exposure,  being  now  3  cm.  to  the  other  side  (the  left) 


THE  CROSS-THREAD  METHOD  33 

of  the  vertical.  The  second  exposure  is  then  made. 
Alternatively,  the  first  exposure  may  be  made  with 
the  central  ray,  the  anode  being  vertical  with  the 
intersection,  and  the  tube  be  moved  6  cm.  to  one  side 
for  the  second  exposure. 

Interpreting  the  Negative. — When  these  plates  are 
developed,  the  wires  show  as  clearly  defined  white 
lines  across  each  plate.  Supposing,  for  simplicity,  a 
round  bullet  be  present  in  the  tissues,  its  position  in 
relation  to  the  wires,  even  on  the  flat,  will  be  found  to 
be  dissimilar  in  the  two  negatives.  In  order  to  deter- 
mine the  position  of  the  bullet,  and  so  interpret  these 
negatives  properly,  the  simplest  method  is  to  recon- 
struct geometrically  the  relations  which  existed 
between  the  tube  and  the  cross  wires  when  the 
photographs  were  taken.  This,  again,  if  one  is 
familiar  with  the  principles,  can  be  carried  out  in  a 
variety  of  ways,  but  the  most  satisfactory  method  is 
to  have  a  small  table  with  a  thick'  plate-glass  top, 
into  the  glass  of  which  there  has  been  cut  with  a 
diamond  two  lines  at  right  angles  to  each  other, 
intersecting  in  the  middle  of  the  plate  (Fig.  25).  The 
vertical  support  has  a  shding  T-piece,  with  three  httle 
notches  3  cm.  apart.  The  middle  notch  is  adjusted 
to  be  at  right  angles  to  the  point  where  the  two  lines 
intersect.  This  can  be  made  to  slide  up  and  down, 
and  be  fixed  in  any  position,  so  that  the  exact  distance 
between  the  middle  notch  and  the  glass  plate  can  be 
arranged  to  be  precisely  the  same  as  was  the  distance 
between  the  anode  of  the  tube  and  the  cross  wires 
when  the  X-ray  photographs  were  taken.  As  stretched 
threads  can  be  made  to  represent  the  linear  path  of 
X  rays,  the  paths  of  any  of  the  rays  with  which  one 
is  dealing  can  be  dehneated  by  placing  fine  threads 

3 


34     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

into  each  of  the  two  notches,  the  threads  being- 
weighted  at  one  end  so  as  to  be  kept  taut,  while  the 
other  end  is  fixed  to  a  fine  needle.  As  some  workers 
prefer  to  displace  the  tube  to  lo  cm.  instead  of  6,  a 
small  extension  has  been  added  to  the  T-piece.     This 


Fig.  25. 

extension  is  shown  in  the  illustration  as  a  projecting 
piece  beyond  the  portion  where  the  cross  threads  are 
suspended.  In  the  diagrammatic  representation  of 
the  T-piece  (Fig.  27),  there  is  shown  a  horizontal  scale 
which  enables  the  operator  to  deal  with  any  reasonable 
displacement  he  chooses  to  make. 

The  Cross-thread  Method. — The  cross  wires  are  so 
close    to    the    photographic    plate    that    they    suffer 


THE  CROSS-THREAD  METHOD  35 

practically  no  displacement,  but  assuming  that  the 
bullet  is  at  some  depth  from  the  surface  of  the  skin 
which  is  resting  upon  the  cross  wires,  this  will  show  a 
certain  amount  of  displacement,  or,  as  it  is  called, 
parallax.  If,  however,  upon  some  transparent  material, 
like  celluloid  or  tracing  paper,  two  lines  are  drawn  at 
right  angles  to  each  other,  the  image  of  these  lines 
can  be  so  placed  over  the  negative  that  they  and  the 
shadow  of  the  cross  wires  are  brought  into  register, 
and  while  thus  maintained,  the  shadow  of  the  bullet 
can  be  marked  or  traced  on  the  transparent  material. 
The  process  is  repeated  for  the  other  negative,  using 
the  same  piece  of  celluloid  or  tracing  paper. 

Instead  of  the  tracing  being  made  directly,  the 
same  result  may  be  obtained  by  drawing  the  cross 
lines  on  a  sheet  of  paper  or  stiff  cardboard,  and  the 
position  of  the  bullet  may  be  marked  by  means  of 
compasses,  the  vertical  distance  of  the  two  wires  from 
the  centre  of  the  bullet  being  taken.  Once  this 
position  has  been  obtained  for  the  two  negatives,  it 
is  placed  upon  the  glass  stage,  and  the  cross  lines 
are  brought  into  exact  register  and  fixed  in  that 
position. 

It  is  important  in  this  connection  to  point  out  that 
the  wires  upon  which  a  patient  is  rested  should  be 
inked,  so  as  to  leave  a  mark  of  their  position  on  the 
skin.  Further,  a  mark  must  be  made  in  one  of  the 
quadrants  formed  by  the  cross  wires  on  the  patient's 
skin,  and  on  the  same  situation  a  small  piece  of  lead 
wire  should  be  placed,  so  as  to  enable  the  surgeon  to 
learn  in  which  of  the  quadrants  the  foreign  body  is 
situated.  When  the  tracings  from  the  negative  are 
taken,  it  is  very  important  to  identify  the  position  of 
the  marked  quadrant. 


36     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

We  now  have  a  reproduction  of  the  shadow 
pictures  in  the  exact  geometrical  position  in  which  they 
were  produced.  It  is  obvious  that  the  shadow  of  the 
bullet  which  is  more  to  the  observer's  left  must  have 
been  produced  by  the  tube  when  it  was  in  the  position 
more  to  the  observer's  right.  Therefore,  a  thread  can 
be  placed  in  the  appropriate  notch,  and  the  needle 
end  attached  to  any  position  within  the  bullet  shadow — 
e.g.,  the  centre.  This  being  done,  it  follows  that  the 
bullet  must  have  had  its  centre  at  some  point  along 
the  line  indicated  by  the  thread.  If,  now,  a  second 
thread  be  placed  in  the  other  notch,  separated  6  cm. 
from  the  first,  it  will  represent  the  position  of  the  anode 
when  the  second  negative  was  made,  and  can  be  placed 
upon  the  centre  of  the  corresponding  shadow  of  the 
bullet.  Here,  again,  the  centre  of  the  bullet  must 
have  been  situated  at  some  point  along  the  course 
of  the  straight  line  indicated  by  the  stretched  thread, 
and  the  point  where  the  two  threads  thus  fixed  cross 
each  other  must  be  the  exact  position  of  the  centre 
of  the  bullet.  Such  is  the  essence  of  the'  theory 
of  what  is  known  as  the  cross-thread  method  of 
localization. 

The  Three  Co-ordinates. — The  question  now  remains 
as  to  the  method  of  ascertaining  the  position  of  this 
crossing  of  the  threads  in  relation  to  the  patient's 
body.  Here  we  must  revert  to  what  has  already  been 
said  about  the  three  co-ordinates  in  reference  to  the 
three  planes.  The  distance  of  the  intersection  of  the 
threads  from  the  fiat  horizontal  plane  is  first  measured. 
This  is  the  Z  co-ordinate,  and  actually  represents  the 
exact  depth  of  the  centre  of  the  bullet  from  the  part 
of  the  patient's  skin  which  rested  upon  the  photo- 


THE  CROSS-THREAD  METHOD 


37 


graphic  plate.     How  shall  this  position  on  the  patient's 
skin  be  determined  ? 

The  position  is  ascertained  in  the  following  manner : 
The  cross  wires  are  to  represent  the  basis  of  the  vertical 
planes.  For  example,  if  one  is  inspecting  the  site  upon 
which  a  building  is  to  be  erected,  and  the  position 


Fig.  26.' 

A  "  ghost."'  or  double-exposure  photograph,  which,  when  viewed  in  the  stereo- 
scope, helps  to  visualize  the  fact  that  the  mark  of  the  cross  wire  on  the 
patient's  skin  forms  the  base  of  planes.  The  position  of  the  bullet  is 
ascertained  by  the  vertical  distance  from  these  planes,  and  from  the  skin 
of  the  arm  on  which  the  photographic  plates  rested. 

of  the  walls  is  chalked  out  on  the  earth,  one  can  quite 
well  conceive  the  chalk  lines  as  the  base  of  a  vertical 
plane,  although  the  walls  are  not  actually  in  existence. 
In  the  same  manner,  a  vertical  plane  may  be  erected 
upon  these  wire  shadows  most  conveniently  by  means 
of  a  centimetre  measure  mounted  on  a  rectangular 
horizontal  base.  In  this  way  the  edge  of  the  base 
can  be  brought  into  register  with  the  line,  and  then  the 
vertical  distance  from  the  face  of  this  vertical  plane 
to  the  point  of  intersection  of  the  cross  wires  can  be 
accurately   measured. ^     By   repeating   the   procedure 

^  AMa:iual  of  X-Ray  Technic,  by  A.  C.  Christie  (J.  B.  Lippincott). 
Description  of  alternative  plan  of  marking  a  spot  on  tracing  vertical 
below:  first,  where  threads  cross,  and  then  measuring  co-ordinate 
directiv  from  the  lines. 


38     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

for  the  other  planes,  we  arrive  at  the  three  co-ordinates, 
X,  Y,  and  Z,  of  the  point  in  question. 

These  data  obtained,  we  go  to  the  patient,  and 
examining  the  marks  made  by  the  wires  upon  his  skin, 
we  learn  in  what  quadrant  the  bullet  is  situated  by 
means  of  the  mark  already  mentioned.  Were  it  not 
for  some  such  means  of  identification,  there  might  be 
disaster.  If  the  patient  had  his  hand  or  arm  resting 
upon  the  plate,  for  example,  the  tube  being  above, 
then  the  mark  of  the  cross  wires  on  the  palm  when 
the  back  of  the  hand  was  inspected  would  be  reversed 
in  relation  to  the  measurements  already  mentioned 
when  the  hand  was  turned  over  and  an  examination 
made  of  the  palm.  The  two  quadrants  which  were 
towards  the  inner  side  of  the  foreign  body  would  now 
be  turned  towards  the  outer  side.  Although  this  is 
so  very  obvious,  a  lamentable  error  in  this  respect 
might  readily  occur  if  special  precautions  are  not 
taken. 

All  that  now  remains  to  be  done  is  to  take  the  two 
co-ordinates,  Y  and  X,  and  measure  them  on  the 
skin  from  the  respective  planes.  Premising  that  the 
hand,  etc.,  is  placed  in  such  a  position  that  the  vertical 
direction  can  be  ascertained — which  is  a  very  important 
consideration — the  points  where  these  co-ordinates 
meet  fixes  the  point  on  the  patient's  skin  below  which 
vertically,  at  the  distance  Z,  the  centre  of  the  bullet 
is  situated.  This  distance  is  conveniently  measured 
by  a  little  surface  gauge  shown  in  the  illustration  with 
the  pointer  at  the  intersection  of  the  cross  wires. 

At  the  risk  of  some  recapitulation,  the  reader  may 
be  invited  to  study  this  procedure  in  a  specific  case  as 
diagrammatically  illustrated  in  Fig.  27,  which  repre- 
sents the  original  diagrams  produced  when  the  author 


THE  CROSS-THREAD  METHOD 


39 


Fig.  27A. 


Marked 

Ouadrant 


Depth  5  cm 


Defjr.-?-'^'" 


Fig.  27B. 


40     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

first  published  his  method  in  1898.  In  Fig.  27A  the 
negative  is  shown  lying  on  the  table  with  the  glass  side 
uppermost;  the  scale  above  the  table  is  fixed  at  a  height 
equal  to  that  of  the  anode  when  the  negative  was  taken. 
The  threads  are  introduced  into  notches  in  the  scale 
6  cm.  apart,  being  kept  taut  by  weights,  as  already 
described,  and  their  other  ends  are  threaded  into  fine 
needles,  fixed  into  the  mouse-shaped  pieces  of  lead 
(M,M). 

Suppose  we  are  dealing  with  a  needle  in  some  part 
of  the  body.  On  taking  two  exposures  on  the  same 
plate,  and  looking  down  on  the  negative,  we  find 
images  of  two  needles;  as  the  tube  was  displaced  hori- 
zontally in  a  line  running  right  and  left,  the  shadow  of 
the  needle  to  the  left  was  evidently  produced  by  the 
tube  when  displaced  to  the  right,  and  vice  versa.  Thus, 
if  one  of  the  threads  be  placed  on  the  point  of  the  needle 
in  one  shadow  correctly,  it  will  indicate  the  path  of  the 
ray  which  produced  the  shadow  of  the  needle-point 
(P) ;  and  if  the  other  thread  is  placed  on  the  corre- 
sponding point  of  the  second  needle  shadow  (P^),  it 
must  follow  that  the  position  actually  occupied  by  the 
point  of  the  needle  in  question  is  precisely  where  the 
two  threads  cross  at  C. 

The  three  co-ordinates  of  the  point  in  question  (C) 
can  be  quickly  ascertained.  The  vertical  distance 
from  the  negative  to  where  the  points  cross  each  other 
is  first  measured  with  an  ordinary  pair  of  compasses 
or  with  a  surface  gauge.  This  is  the  distance  of  the 
point  of  the  needle  beneath  the  skin  (of  the  patient) 
which  rested  on  the  photographic  plate.  The  small 
arrow  in  Fig.  27 A  represents  the  marked  quadrant, 
and  2,  3,  and  4  mark  the  other  corners  of  the  negative. 

We  next  measure  the  vertical  distances  from  the 


THE  CROSS-THREAD  METHOD  41 

two  vertical  planes  represented  by  the  shadows  of  the 
cross  wires  to  the  point  where  the  threads  cross.  An 
upright  square  is  placed  with  its  edge  coincident  with 
the  shadow  of  one  of  the  wires,  and  the  perpendicular 
distance  is  measured  with  compasses  from  it  to  the 
'  point  where  the  threads  intersect.  We  have  now  ob- 
tained our  X,  y,  and  Z  co-ordinates  of  the  point  of 
the  needle,  and  we  note  the  result  down,  as  shown  in 
Fig.  27B.  The  arrows  here  indicate  the  direction  of 
the  displacements  of  the  tube.  We  then  proceed  in  a 
similar  manner  to  ascertain  the  position  of  the  e^'e  of 
the  needle  (C^  in  Fig.  27A),  and  the  distance  between 
C  and  C^  gives  the  needle's  direction  and  actual  length. 
From  the  measurements  jotted  down,  as  shown  in 
Fig.  27B,  we  can  mark  a  line  on  the  patient's  skin  in 
the  same  plane  as  the  needle,  and  give  the  surgeon  the 
exact  depth  at  which  each  of  its  extremities  can  be 
reached  by  a  vertical  puncture. 


CHAPTER  VI 

PRECISE  localization:  further  considerations 

Application  to  the  Screen.— The  method  described 
in  the  previous  chapter  can  be  made  purely  a  fluorescent 
screen  method,  and  adopted  without  the  necessity  for 
employing  a  photographic  plate  at  all.  The  foreign 
object  or  objects,  however,  must  be  clearly  visible 
on  the  screen.  The  procedure  is  identical  with  the 
foregoing  up  to  the  point  at  which  the  photographic 
plate  is  introduced.  Instead  of  the  plate,  attention 
must  be  turned  to  the  screen,  on  which  the  intersecting 
lines  must  be  clearly  indicated,  either  by  a  mark  on 
the  glass  itself,  or  by  stretched  opaque  threads  over 
a  piece  of  tracing  paper  or  film,  which  should  be  lightly 
attached  to  the  glass  covering  of  the  screen  by  means 
of  plaster  at  the  corners.  If  the  adjustments  of  the 
tube  are  made  so  that  the  vertical  distances  from  the 
cross  wires  are  all  calculated,  as  already  described, 
the  shadow  of  the  foreign  body  can  be  traced  and  the 
displacement  carried  out  in  the  same  manner  as  when 
using  the  plates.  When  the  tube  is  excited,  the  screen 
should  be  moved  about  until  the  cross  lines  on  the 
tracing  paper  come  into  exact  register  with  the  shadow 
caused  by  the  cross  wires  which  are  on  the  patient's 
skin.  In  this  position,  with  a  pencil  of  a  particular 
colour  (red  or  black),  the  shape  and  position  of  the 
foreign    bodies    are     outlined    on    the    tracing-paper. 

42 


PRECISE  LOCALIZATION  43 

Then,  the  whole  of  the  screening  arrangement  being 
kept  securely  in  the  same  position,  the  tube  is  displaced 
by  6  cm.  from  the  middle  point  along  one  of  the  cross 
wires.  A  displacement  in  the  shadows  of  the  foreign 
bodies  is  at  once  visible,  and  their  new  position  is 
outlined  by  a  pencil  of  a  different  colour  (black  or  red) . 
With  an  apparatus  which  will  allow  of  the  ready 
adjustment  of  the  position  of  the  tube,  this  work  can 
be  done  in  a  few  minutes,  and  the  tracing  so  obtained 
can  be  placed  upon  the  cross-thread  localizer,  and  the 
exact  position  and  size  of  the  foreign  bodies  ascertained 
forthwith.  If  the  principle  of  the  method  is  thoroughly 
grasped,  the  apparatus  and  technique  for  carrying  it 
out  are  matters  for  the  individual  worker  to  devise. 
This  procedure,  of  course,  saves  time  as  well  as  plates, 
and,  if  the  tracing  be  carefully  done,  the  measurements 
are  approximately  exact. 

A  Stereoscopic  Result. — Even  if  the  photographic 
method  be  employed,  an  economy  in  plates  can  be 
effected  b}^  using  only  one  plate  for  the  tw^o  exposures. 
Two  tracings,  each  corresponding  to  one  of  the  ex- 
posures, can  then  be  taken  from  this  plate,  and  a 
diagrammatic  stereoscopic  picture  can  be  made  which 
will  show  the  relative  position  of  the  foreign  bodies 
to  each  other  and  to  the  cross  wires.  It  is  always 
important  to  remember  that  by  this  localization  method 
the  two  images,  whether  from  the  photographs  taken 
on  two  separate  plates,  or  from  the  two  tracings  taken 
from  the  two  exposures  on  a  single  plate,  can  be  com- 
bined so  as  to  form  a  stereoscopic  result.  The  subject 
of  X-ray  stereoscopy  has  been  dealt  with  in  another 
chapter,  but  it  is  as  well  to  mention  here  that  this 
stereoscopic  use  of  the  results  of  the  localization 
method  is  of  considerable  advantage  to  the  surgeon, 


44     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY     . 

since  not  only  does  the  localization  method,  pure  and 
simple,  give  him  material  for  exact  measurements, 
but,  if  he  possesses  binocular  vision,  the  stereoscopic 
relief  will  enable  him  to  visualize  the  relative  position 
of  the  cross  wires  and  the  bones  of  the  patient  to  the 
foreign  body.  As  the  surgeon  is  more  accustomed, 
naturally,  to  operate  from  anatomical  relations  than 
from  vertical  planes  and  co-ordinates,  it  is  very 
fortunate  that  he  can  have  this  general  stereoscopic 
view  of  the  parts  before  and  during  operation,  as 
well  as  the  exact  measurements,  to  guide  him.  It  is 
possible,  with  the  stereoscopic  view,  by  placing  a 
piece  of  wire  of  known  length  upon  the  patient's 
skin,  to  estimate  more  ^  or  less  roughly  the  various 
distances  of  the  foreign  bodies  from  each  other  and 
from  any  of  the  points  in  the  view. 

The  marking  of  the  cross  wires  on  the  patient's 
skin  can  be  conveniently  done  with  nitrate  of  silver, 
and  the  point  below  which  the  foreign  body  is  situated 
can  also  be  marked  with  the  same  chemical.  This 
has  the  advantage  of  marking  the  skin  distinctly,  and 
of  not  being  readily  obliterated  by  the  necessary 
antiseptic  washings  and  other  procedures  which  are 
taken  before  the  actual  operation  for  the  removal  of 
the  foreign  body.  An  exception  is  to  be  noted  in 
the  case  of  iodine,  which  will  obliterate  the  silver 
markings.  It  is  important  to  take  careful  notes  of 
the  position  of  the  patient's  body  when  the  photo- 
graphic or  screen  examination  is  being  made.  In  the 
leg,  for  example,  the  weight  of  the  resting  limb  dis- 
places the  soft  parts,  and  it  is  well,  when  the  limb  is 
in  position,  to  mark  with  a  surface  gauge  a  horizontal 
line  on  the  leg,  and  to  note  the  vertical  distance  to 
the   photographic    plate,    because   the   measurements 


PRECISE  LOCALIZATION  45 

one  obtains  give  the  distance  below  the  skin  when  the 
leg  is  in  that  position.  If  the  removal  of  the  foreign 
body  is  to  be  carried  out,  the  release  of  the  limb  from 
pressure  would  alter  the  distance  between  the  point 
on  the  skin  and  the  depth  at  which  the  foreign  body 
is  lying.  It  follows  that  any  landmark  placed  upon 
the  surface  of  the  skin,  such  as  lead  wire  or  lead  foil 
arrows,  will  permit  of  the  measurements  being  made 
with  reference  to  this  fixed  point,  and  in  this  way 
the  trouble  due  to  a  difference  of  position  is  obviated, 
and  the  exact  distance  of  the  foreign  body  can  be 
determined  from  any  point  on  the  patient's  skin 
which  the  surgeon  may  select  as  the  most  convenient 
starting-place  for  operation.  A  little  bismuth  oint- 
ment on  the  skin  is  a  convenient  means  of  demon- 
strating stereoscopically  the  relation  of  the  skin  to 
the  parts  beneath. 

Other  Uses  of  the  Method. — The  method  which  has 
been  described  in  a  general  way,  and  for  one  particular 
class  of  foreign  bodies,  is,  of  course,  equally  applicable 
to  other  classes.  In  the  case  of  a  needle,  for  example, 
the  method  will  furnish  information  as  to  the  exact 
position  of  either  end  of  the  needle,  as  well  as  its  exact 
length,  and  the  angle,  often  very  oblique,  at  which 
it  is  situated.  The  method  can  also  be  used  for 
ascertaining  the  exact  size  and  position  of  any  organ 
the  shadow  of  which  can  be  differentiated.  For  ex- 
ample, by  means  of  tracings  of  the  bones  of  the  pelvis 
taken  in  the  way  described,  and  then  tracings  from 
the  two  negatives  placed  on  the  cross-thread  localizer, 
the  two  needles  carrying  the  threads  being  placed 
upon  the  corresponding  points,  the  exact  size  of  the 
pelvis  can  be  ascertained.  The  results  of  such  a 
method  would  be  much  more  accurate  for  gyn^colo- 


46     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

gists,  not  to  speak  of  being  obtained  more  simply,  than 
any  results  based  upon  external  measurements.  The 
exact  size  of  the  heart  could  be  demonstrated  in  the 
same  manner. 

Naturally,  it  involves  some  little  practice  and  time 
for  the  mind  to  become  familiar  with  the  practical 
applications  of  the  co-ordinates  from  known  planes 
of  reference,  but  it  is  well  worth  acquiring,  for  it  places 
in  the  hands  of  the  X-ray  worker  what  practically 
amounts  to  an  infallible  method  of  getting  all  the 
necessary  information  as  to  the  size  and  position  of 
foreign  bodies  and  their  relations  to  the  surface. 


CHAPTER  VII 

LOCALIZATION    OF   FOREIGN    BODIES    IN   EYEBALL 
AND    ORBIT 

Precision  Essential. — The  method  of  localization 
described  in  the  preceding  chapters  can  be  applied 
in  ophthalmology  with  very  gratifying  results.  Pre- 
cision in  localization  is  important,  whatever  the  part 
of  the  body  with  which  one  may  be  dealing,  but  it  is 
essential  in  the  case  of  so  delicate  a  structure  as  the 
ej^eball,  where  the  slightest  deviation  from  accuracy 
may  involve  the  loss  of  vision.  The  principles  con- 
cerned in  the  localization  of  foreign  bodies  in  the  eyeball 
and  orbit  are  the  same  as  those  which  have  already 
been  described,  but  if  the  method  is  to  be  carried  out 
successfully,  attention  must  first  be  paid  to  certain 
practical  adjustments. 

Arrangement  of  Patient. — The  first  point  of  impor- 
tance is  that  the  patient  must  be  in  a  sitting  posture, 
that  the  head  must  be  kept  rigid,  and  the  eyeball  under 
examination  never  allowed  to  move  in  the  slightest 
degree  while  the  photograph  is  being  taken.  This, 
like  the  method  of  more  general  application,  can  be 
carried  out  in  a  variety  of  ways.  In  the  method 
which  the  author  has  adopted,  an  apparatus  is  employed 
which  is  known  as  the  headpiece,  and  is  clamped  on 
to  a  table.  The  headpiece  consists  of  a  rigid  frame  of 
wood,  with  a  space  cut  into  it  of  sufficient  size  to 
admit  a  photographic  half-plate.     Across  this  space 

47 


48     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

two  intersecting  wires  (piano  wires  will  serve)  are 
stretched,  one  vertically,  and  the  other  horizontally. 
The  patient,  while  sitting  upright  in  a  chair  which 
can  be  raised  and  lowered  like  a  piano  stool,  rests  the 
temple  of  the  side  under  examination  against  these 
cross  wires,  and  the  back  of  the  head  is  supported  by 
a  piece  of  board  fastened  at  right  angles  to  one  of  the 
wires.  On  the  opposite  side  of  the  head  to  that  under 
examination,  a  second  piece  of  board,  with  a  thumb- 
screw sliding  in  a  groove,  serves  to  press  and  fix  the 
head  laterally  against  the  two  stretched  wires,  and  the 
chin  is  supported  on  an  adjustable  projection.  As 
an  alternative  method  of  producing  steadiness,  an 
adjustable  horizontal  bar  can  be  used,  which  the 
patient  may  hold  with  his  teeth.  The  arrangement,  as 
just  described,  is  illustrated  in  Fig.  28.  There  is  no 
upholstery  about  this  contrivance;  it  is  all  of  wood, 
and  admits  of  no  shifting  of  the  patient.  The  adjust- 
ment of  the  anode  of  the  tube  at  right  angles  to  the 
intersection  of  the  piano  wires  is  facilitated  by  fixing 
a  rifle  ''  sight  "  (Fig.  29)  very  correctly,  so  as  to  have 
its  point  at  right  angles  on  the  same  level  as  the  point 
of  intersection.  To  improve  the  definition  of  the  tube 
a  sheet  of  fairly  thick  lead  rubber^  with  a  hole  about 
3  cm.  in  diameter  punched  in  its  centre,  can  be  sus- 
pended on  a  sliding  bar  in  such  a  way  that  this  stop 
can  rest  against  the  tube  and  be  so  adjusted  as  to 
admit  a  small  cone  of  X  rays  through  the  aperture. 
This  apron  stop,  being  attached  to  a  sliding  bar,  slides 
parallel  to  the  movement  of  the  tube,  and  can  be 
easily  adjusted  when  the  tube  is  displaced.  Although 
not  absolutely  essential,  it  greatly  improves  the  defi- 
nition of  the  photographs,  as  it  cuts  off  all  the  scat- 
tered radiation  from  the  glass. 


PLATE  XI. 


Fig.  28. — Head-Rest  for  Eve  Localization. 


Fig,  29. — The  Shadow  of  the  Piano  Wires  obtained  on  a 
Photographic  Plate  which  was  put  up  against  the 
Rifle  Sight,  showing  that  the  i\NODE  of  the  Tube 
has  been  accurately  centred, 


To  face  Jj.  48. 


PLATE  XII. 


Fig.  30.  — Head-Rest  for  Eye  Localization  with  Patient  in 

Position. 


Fig.  31. — Side  View  of  Head-Rest. 


{_To  face  p.  48. 


FOREIGN  BODIES  IX  EYEBALL  AND  ORBIT  49 

Position  of  Tube. — The  tube  is  held  in  a  sliding 
support,  and  adjusted  carefully,  so  that  the  fine  point 
of  the  anode  from  which  the  linear  rays  originate 
is  at  right  angles  to  the  point  of  intersection  of  the 
wires.  When  it  has  been  approximately  so  placed, 
it  can  be  excited,  and  with  a  fluorescent  screen  close 
up  against  the  rifle  "  sight,"  the  exact  central  position 
of  the  tube  can  be  secured  b\-  bringing  the  shadow  of 
the  point  where  the  wdres  intersect  right  into  line  with 
the  ''sight"  (as  in  Fig.  28).  The  distance  between 
anode  and  intersection,  usually  42  cm.,  is  carefully 
noted.  Some  definite  mark — a  small  black  spot  on 
a  piece  of  rubber  plaster,  hke  a  buU's-e^ve  on  a  target, 
answers  well — is  placed  at  some  distance  in  front  of 
the  patient  in  such  a  position  that,  when  he  is  fixing 
his  gaze  upon  it,  the  eye  under  examination  has  its 
visual  axis  parallel  to  the  horizontal  piano  wire.  The 
patient  being  in  position,  and  the  vertical  mre  in 
advance  of  his  eye,  the  position  of  the  horizontal 
wire  can  be  marked  upon  his  temple.  Another  very 
important  point  is  the  placing  of  a  piece  of  lead  wire 
or  foil,  I  cm.  in  length,  on  the  patient's  lower  eyelid, 
as  close  to  the  eyeball  as  possible  (Figs.  30  and  31) .  The 
position  of  this  landmark,  which  can  be  secured  in 
place  bv  two  strips  of  adhesive  plaster,  has  then  to  be 
most  carefuUy  noted  in  relation  to  the  eyeball  itself 
when  the  patient  under  examination  is  gazing  at  the 
fixed  point.  It  is  necessary  to  discover  whether  this 
identification  mark  is  vertically  below  the  centre  of 
the  cornea,  or  behind,  or  in  advance  of  that  plane;  also, 
how  many  millimetres  it  is  to  the  right  or  left  of  the 
vertical  line  through  the  middle  of  the  cornea,  and  how 
far  below  the  corneal  centre. 

One  very  simple  addition  which  the  author  has 

4 


50     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

lately  made  to  this  method,  and  which  is  the  final 
adjustment  so  far  as  the  patient  is  concerned,  consists 
of  a  loop  of  fuse  wire  with  a  prolongation  to  serve  as 
a  holder,  in  the  manner  depicted  in  Figs.  32  and  33. 
The  loop  is  of  such  size  and  shape  as  to  fit  into  the 
orbital  cavity,  and,  once  it  is  in  place,  the  globe  of  the 
e3'e  is  maintained  perfectly  rigid  during  examination. 
It  is  placed  over  the  eyelids,  which  are  slightly  open, 
and  with  gentle  but  firm  pressure  the  eye  is  ''  fixed  " 
in  the  position  of  gazing  at  the  "bull's-eye  mark." 
An  X-ray  photograph  of  the  eye,  obtained  with  this 
arrangement  in  position  is  reproduced  in  Fig.  34. 
Absolute  immobility  is  now  secured. 

Displaced   Negatives. — The  photographic  plate  in 

its  usual  paper  envelope  is  placed  against  the  piano 
wires,  which  should  be  in  contact  with  the  patient's 
temple,  and  is  kept  in  position  by  means  of  a  hinged 
lid.  The  tube  is  then  displaced  in  the  usual  way,  in 
the  plane  exact!}'  parallel  with  the  horizontal  wire, 
3  cm.  to  one  side  of  the  central  or  zero  position,  and 
3  cm.  to  the  other,  and  an  exposure — on  a  separate 
plate,  of  course — is  made  at  each  displacement. 
From  the  two  negatives  tracings  are  taken  as  before, 
and  the  geometrical  relations  worked  out  on  the  cross- 
thread  localizer.  The  point  of  importance  here  is 
that  the  worker  is  enabled  to  arrive  at  the  exact 
relation  of  the  foreign  body  or  bodies  to  the  point  of 
wire  nearest  the  eyeball — first,  by  ascertaining  the 
three  co-ordinates  of  this  known  point;  then  the  three 
co-ordinates  of  the  unknown  foreign  body;  and,  finally, 
by  making  a  simple  subtraction.  These  measurements 
being  noted  down,  a  convenient  method  of  obtaining 
the  position  of  the  foreign  body  is  to  take  a  model 
eye,  five  times  larger  than  the  average  human  organ 


PLATE   XIII. 


Fig.  32. — Showing  Loop  of  Wire  to  keep  Eye  IxMiMobile,  also  to 
FACILITATE  LOCALIZATION  (^See  FiGS   34  and  58). 


Fig.  33. — Method  of  fastening  Indicator  Wire  to  Lower  Eyelid. 

[To  face  p.  50. 


PLATE    XIV. 


^^^^^^^^H 

r 

1 

■ 

Fig.   3^. — X-Ray  Photograph  of  Eye  with  Loop  in  Position 

(See  Fig.  32). 


Fig  35. — "Ghost"  Photograph  of  Model  Eye  placed  in  Head- 
piece, to  illustrate  that  the  Stretched  Piano  Wires  form 
the  Basis  of  Planes  from  which  Co-ordinates  can  be 
measured. 


[To  face  p.  50 


FOREIGN  BODIES  IN  EYEBALL  AND  ORBIT         51 

(Fig.  35),  and  then,  by  means  of  a  surface  gauge,  to 
so  adjust  its  point  of  wire  as  to  reproduce  on  the  model 
eye  the  relationship  which  the  same  identification  mark 
bore  to  the  eye  of  the  patient.  The  co-ordinated 
measurements  are  then  applied,  and  it  is  noted  that  the 
foreign  body  is  situated  so  many  millimetres  above  or 
"below  this  landmark,  so  many  millimetres  to  the  right 
or  left,  and  so  many  millimetres  directly  backwards 
parallel  to  the  visual  axis.  In  this  manner  the  position 
of  the  foreign  body  in  the  eyeball,  however  small  that 
hody  may  be,  can  be  ascertained  with  great  accuracy, 
and  its  size  also  can  be  determined.  Figs.  35  and  36 
show  the  model  eye  and  the  human  eye  respectively, 
bisected  by  planes  (the  images  being  obtained  by  double 
exposure),  so  that  the  position  of  any  foreign  body 
could  be  measured  in  relation  to  these  imaginary 
planes.  Fig.  37  is  an  attempt  to  show,  also  by  double 
exposure,  the  X-ray  tube  in  position,  and  the  head  of 
the  patient  beyond. 

A  Stereoscopic  Result. — In  this  case,  again,  the 
pictures  thus  obtained  give  stereoscopic  relief,  and 
when  view^ed  either  in  the  Wheatstone  stereoscope  or 
by  converging  the  visual  axes,  and  so  fusing  the 
pictures,  a  single  image  in  relief  is  seen,  giving  the 
relative  position  of  the  parts.  Further  confirmation 
of  the  position  of  the  foreign  body  can  be  obtained 
by  keeping  the  tube  in  a  known  position — say  central 
to  the  central  point — and  taking  two  photographs, 
either  on  the  same  plate  or  on  tw^o  different  plates,  the 
eyeball  being  made  to  look  first  in  one  position  and 
then  in  another  at  a  known  angle  to  the  first — say 
vertically  downwards,  at  an  angle  of  45  degrees  from 
the  horizontal,  or  vertically  upwards  at  an  angle  of 
45  degrees,  or  laterally  to  the  right  or  left  at  an  angle 


52     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

which  is  to  be  noted.  When  the  tracings  from  the 
displacement  of  the  shadow  of  the  foreign  body  are 
made,  its  depth  being  previously  ascertained  by  localiza- 
tion measurements,  the  degree  of  movement  of  the 
foreign  body  in  relation  to  the  centre  of  rotation  of 
the  eyeball  is  obtained,  the  centre  of  rotation  of  the 
eyeball  being  taken  as  a  point  lo  mm.  in  front  of  the 
centre  of  the  retina. 

An  Example  in  Detail. — Although  the  principle  and 
method  of  localization  have  alread}^  been  expounded 
as  fully  as  possible^  the  application  to  a  particular  case 
may  still  seem  to  present  difficulties.  The  author  has 
judged  it  well,  therefore,  to  take  a  specific  instance, 
and  describe  the  whole  procedure  from  beginning  to 
end,  even  wi1h  painstaking  minuteness  and  some  re- 
petition. If  the  directions  in  this  example  case  are 
studied  carefully,  the  worker  should  be  able  to  apply 
them  without  difficulty  to  the  case  with  which  he  is 
actually  dealing,  making,  of  course,  the  modifications 
which  the  different  conditions  of  every  individual  case 
require. 

The  case  selected  is  that  of  a  gentleman  who,  while 
shooting,  was  struck  in  the  right  eye  by  a  pellet.  The 
accident  occurred  about  a  week  before  he  came  for 
X-ray  examination.  The  shot  had  been  fired  at  about 
sixty  3'ards.  The  interior  of  the  eyeball  was  full  of 
blood,  and  the  patient  could  just  perceive  the  differ- 
ence between  light  and  darkness.  The  question  to  be 
decided  was  whether  the  pellet  was  inside  the  eyeball, 
in  which  case  the  eye  would  have  to  be  excised. 

The  X-ray  tube  was  carefully  "  centred  ''  in  the 
headpiece  already  described,  and  a  small  piece  of  fuse 
wire  was  fixed  to  the  patient's  lower  eyelid  with  rubber 
plaster.     The  upper  end  was  on  a  level  with  the  nasal 


PLATE  XV. 


Fig.  36. — "Ghost"  Photograph  with  Head  ix  Position  for 
Localization,  showing  Intersecting  Planes  :  viewed  from 
Tube  Side. 


Fig.  37. — "Ghost"  Photograph  viewed  from  Opposite  Side. 


[To  face  p.  52. 


FOREIGN  BODIES  IN  EYEBALL  AND  ORBIT         53 

end  of  the  horizontal  diameter  of  the  cornea,  but  it 
only  occupied  this  position  when  the  head  of  the  patient 
was  in  the  head-rest,  and  his  eye  was  gazing  steadily 
at  a  small  point  some  distance  in  front  of  him,  placed 
in  such  a  manner  that  the  visual  axis  was  parallel  with 
the  horizontal  piano  wire.  It  was  in  this  position  that 
the  photograph  was  taken.  It  is  of  the  utmost  im- 
portance that  the  patient  should  keep  his  eye  looking 
steadily  at  the  same  point  during  the  two  exposures. 
The  patient  was  placed  in  the  head-rest,  as  already 
described,  the  anticathode  being  42  cm.  from  the  cross 
wires,  and  the  first  exposure  was  made  with  the  tube 
centrally  placed — that  is  to  say,  at  right  angles  to  the 
intersection  of  the  cross  wires.  One  exposure  was  given 
for  about  fifteen  seconds,  and  then  the  plate  was  changed 
without  disturbing  the  position  of  the  patient,  and  the 
tube  was  moved  by  sliding  its  supporting  cage  6  cm. 
backwards,  the  second  exposure  being  then  given.  The 
negatives  were  developed  and  fixed,  and  tracings  were 
taken  from  both  negatives  on  one  piece  of  transparent 
gelatine  tissue.  The  tracings  were  taken  from  the 
glass  side,  a  pencilled  cross  on  the  sheet  of  tracing 
material  being  brought  into  register  with  the  white 
lines  of  the  cross  wires  on  each  negative.  The  two 
images  of  the  indicator  wire  and  of  the  shot  were  traced, 
and  the  tracing  was  then  placed  on  the  stage  of  the 
cross-thread  localizer,  the  cross  being  vertically  below 
one  of  the  end  notches  of  the  small  T-piece.  The  ends 
of  the  cross  threads  were  then  placed  on  the  upper  ends 
of  the  indicator  wire  shadows,  and  the  three  co-ordin- 
ates of  this  point  were  measured  and  noted  down.  In 
the  same  way  the  three  co-ordinates  of  the  shot  were 
ascertained.  Thus  we  decided  the  relative  position 
of  the  shot  to  the  indicator  wire,  and  it  was  found  that 


54     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

the  shot  was  close  to  but  outside  of  the  eyeball ;  indeed,, 
the  position  was  such  that  we  could  assert  confidently 
that  if  our  measurements  were  correct  we  ought  to  be 
able  to  feel  the  shot  against  the  sclerotic.  The  oph- 
thalmic surgeon  who  was  with  the  case  thought  that  the 
shot  could  not  be  felt,  as  he  had  very  carefully  examined 
the  eye  and  could  detect  nothing.  It  was  pointed  out 
to  him  that  shot  often  moved  forwards,  and  the  matter 
was  easier  when  one  knew  the  precise  spot  where  the 
shot  was  situated  and  could  look  for  it  there.  A  few 
drops  of  cocaine  were  dropped  into  the  eye,  and  on 
making  the  patient  look  upwards  at  an  extreme  angle, 
the  finger  being  introduced  gently  into  the  orbit,  the 
shot  could  be  felt  rolling  under  the  finger  up  against 
the  sclerotic.  This  was  next  day  easily  removed,  and 
the  blood  in  the  vitreous  would  gradually  be  absorbed, 
and  the  patient  retain  a  useful  eye.  (This  is  illus- 
trated in  Fig.  54,  Plate  XXIII.) 


APPENDIX  I 

The  Telephone  Attachment  in  Surgery 

The  use  of  the  telephone  as  an  aid  to  the  surgeon  in 
the  detection  of  embedded  bullets  and  splinters  of  shell 
has  gained  considerable  acceptance  since  it  was  brought 
forward  by  the  author  in  a  paper  read  before  the  Medi- 
cal Society  of  London  in  January,  1915.^  It  is  not^ 
however,  offered  as  a  substitute  for  the  X-ray  method^ 
but,  rather,  as  an  additional  procedure,  the  purpose 
of  which  is  to  ensure  that  the  advantage  gained  by  a 
previous  X-ray  localization  is  not  lost  in  the  exigencies 
of  the  actual  surgical  extraction.  The  ideal  plan 
would  be,  first  to  localize  a  foreign  body  by  the  X-ray 
method,  and  then  to  guide  each  step  of  its  removal  by 
means  of  the  telephone. 

The  author's  first  experiments  with  the  telephone 
in  surgery  were  made  in  the  eighties,  soon  after  its  use 
in  this  connection  was  suggested  by  Professor  Graham 
Bell.  It  was  Graham  Bell  who  pointed  out  that  if  a 
probe  were  fixed  to  one  terminal  of  a  telephone  and  a 
plate  of  metal  to  the  other  terminal,  the  plate  being 
laid  on  the  skin  of  the  patient,  a  galvanic  battery  would 
be  formed  within  the  body  whenever  the  probe  struck 
an  embedded  piece  of  metal,  and  the  current  thus  pro- 
duced would  be  sufficient  to  operate  the  telephone 
receiver.  One  condition  laid  down  by  the  American 
electrician,  however,  was  that  the  instrument  attached 

^  Lancet,  January  30,  1915. 
55 


56     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

to  the  one  terminal  must  be  of  the  same  metal  as  the 
plate  attached  to  the  other  terminal,  and  it  is  only 
since  the  war  suggested  a  fresh  recourse  to  the  method 
that  the  author  finds  that  this  condition  is  not  essential 
to  success. 

If  a  steel,  silver,  or  nickel-plated  instrument  is 
attached  to  one  terminal  of  the  telephone,  and  the 
embedded  metal  to  be  sought  for  is  lead,  nickel,  copper, 
iron,  or  certain  of  the  iron  alloys  used  in  shell  manu- 
facture, the  loudest  sound  is  elicited  on  contact  when  a 
carbon  plate  is  attached  to  the  other  terminal.  The 
carbon  plate  which  is  used  in  an  ordinar}^  bichromate 
cell  answers  the  purpose  quite  effectively,  but  it  should 
be  as  large  as  is  convenient.  The  carbon  and  also  the 
patient's  skin  upon  which  it  is  placed  should  be 
moistened  with  a  salt  solution  in  order  that  the  con- 
duction may  be  as  good  as  possible,  and  if  the  skin 
beneath  the  plate  is  brushed  with  an  iodine  solution 
the  result  is  still  more  satisfactory-^  The  currents 
generated  under  this  arrangement  are,  naturally,  ex- 
tremely small,  and  in  consequence  are  better  detected 
by  a  telephone  of  60  ohms  resistance,  or  even  less, 
than  by  the  more  expensive  high-resistance  telephones 
used  in  wireless  telegraphy. 

An  idea  of  the  general  arrangement  can  be  obtained 
from  Fig.  38.  Affixed  to  the  surgeon's  head  are,  pre- 
ferably, double  receivers,  though  a  single  receiver  can 
be  used  if  the  hearing  is  acute.  The  carbon  plate  is 
held  in  position  by  means  of  plaster  or  bandage  upon 
the  patient's  moistened  skin.  To  this,  which  forms 
the  positive  element,  one  terminal  of  the  telephone  is 
attached.  The  other  terminal  is  connected  to  a  lead 
which  is  detachable  for  sterilizing  purposes,  and  need 
only  be  handled  by  the  surgeon  or  his  assistant,  exer- 


APPENDIX  I  57 

cising  the  usual  antiseptic  precautions.  This  section 
of  wire  is  spring-chpped  on  to  the  surgeon's  instrument, 
be  it  knife,  probe,  needle,  or  forceps.  The  foreign 
body  is  the  negative  element,  and  when  the  circuit  is 


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Sensitive 
Receivers 

completed  by  contact  between  the  negative  element 
and  the  positive  element  in  the  shape  of  the  plate,  the 
current  is  produced,  and  an  unmistakable  click  is  heard 
in  the  receiver;  while,  if  the  exploring  instrument  be 
moved  slightly  so  as  to  make  a  rubbing  contact,  the 


58     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

click  becomes  a  sharp  rattle.  This  microphonic  im- 
pression enables  the  surgeon  to  exercise  a  continual 
control  over  the  foreign  body.  The  most  obvious  of 
the  precautions  he  must  take  is  never  to  allow  the  in- 
strument to  which  the  telephone  is  attached  to  come 
in  contact  with  any  other  instrument  already  in  the 
wound,  because  the  sound  thus  created  would  mask 
the  audible  impression  received  from  the  foreign  body. 
The  chief  advantage  of  the  telephone  is  that  in  cer- 
tain respects  it  offers  a  surer  means  of  detection  than 
is  furnished  by  the  surgeon's  own  tactile  sense,  however 
refined  the  latter  may  be.  The  instrument,  for  ex- 
ample, can  distinguish,  as  cannot  be  done  ordinarily 
by  the  sense  of  touch,  between  metal  fragments  and 
pieces  of  fractured  bone.  It  also  enables  the  extrac- 
tion to  be  made  with  the  minimum  of  damage  to  the 
tissues,  and  further  advantages  are  its  simplicity  and 
portability.  A  small  battery  may  be  introduced  into 
the  circuit,  but  in  the  author's  experience  its  advantage 
is  questionable. 

In  ophthalmic  surgery  the  telephone  attachment 
has  been  proved  to  have  a  special  value,  and  several 
cases  could  be  cited  in  which  foreign  bodies  in  the  orbit 
have  been  successfully  extracted  when  the  telephone 
was  employed.  It  is  not  too  much  to  suggest  that  in 
all  cases,  before  enucleating  an  eye  containing  a  foreign 
body  which  is  not  capable  of  being  extracted  in  the 
ordinary  way  with  an  electromagnet,  the  ophthalmic 
surgeon  should  first  attempt  the  removal  of  the  particle 
with  the  assistance  of  the  telephone  attachment. 


APPENDIX  II 

The  Electromagnet  as  an  Aid  to  Localization 

Recently  Professor  Bergonie,  of  Bordeaux/  has  in- 
troduced a  large  electromagnet  as  a  means  of  detecting 
foreign  bodies  embedded  in  the  tissues.  Professor 
Bergonie  has  conceived  the  idea  of  exciting  the  electro- 
magnet by  an  alternating  current  of  1 10-120  or  220- 
240  volts.  If,  under  these  circumstances,  the  magnetic 
field  embraces  the  projectile,  a  vibratory  motion  is 
induced  in  this  latter,  the  vibrations  synchronizing 
with  the  pulsing  of  the  current,  and  having  a  frequency 
generally  between  48  and  55  per  second.  The  magnet 
is,  preferably,  suspended  from  a  wall  bracket,  and  the 
extremity  of  its  core,  in  a  sterilizable  covering,  is  passed 
over  the  suspected  part,  but  is  never  allowed  to  come 
in  contact  with  the  skin.  Any  vibration  in  the  tissues 
is  observed  by  palpating  the  part,  and  this  indicates 
the  presence  of  a  metallic  projectile.  The  point  of 
maximum  vibration  is  then  found  by  more  careful  pal- 
pation, and  the  projectile  accordingly  is  localized  as 
being  nearest  to  the  surface  at  that  point.  Here,  if  it 
is  possible,  the  incision  is  made,  and  the  magnet  again 
used,  followed  by  a  further  digital  exploration,  and  the 
deepening  of  the  incision  in  the  direction  indicated  by 
the  vibrations.  A  very  few  of  these  alternations  of 
procedure,  even  in  the  more  difficult  cases,  usually 
suffice  to  reach  the  foreign  body,  but  the  surgeon  must 

'■  Archives  d'Electricite  Medicate,  May-September,  1915. 

59 


6o     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

take  care  that  the  current  is  switched  off  every  time 
he  uses  his  instruments. 

This  method  at  first  sight,  of  course,  is  only  appHc- 
able  to  the  detection  of  sphnters  of  shell  and  bullets 
of  magnetizable  metal,  thereby  excluding  lead  projec- 
tiles, but  Bergonie  now  states  that  his  electrovibrator 
is  capable  of  inducing  vibration  even  in  non-magnetiz- 
able bodies.  This  is  brought  about  by  eddy  currents 
induced  in  the  metal.  For  this  purpose  a  more  power- 
ful instrument  of  8  or  lo  kilowatts  is  necessary.  Of 
the  non-magnetizable  metals,  aluminium  has  been 
found  to  give  the  most  marked  vibrations,  with  copper 
and  silver  the  next  in  order,  while  it  is  still  difficult, 
unless  the  induction  of  the  instrument  is  largely  in- 
creased, to  bring  about  any  vibration  in  the  case  of 
German  silver,  which  forms  the  sheath  of  revolver 
bullets,  or  of  lead,  which  forms  the  charge  of  shrapnel 
sheU. 

Many  French  military  surgeons  speak  highly  of  the 
method,  which,  it  should  be  clearly  understood,  is 
purely  a  method  of  locaHzation;  the  magnetic  action 
has  no  part  to  play  in  the  actual  removal  of  the  foreign 
body.  The  extraction  is  a  matter  for  the  surgeon's 
fingers  or  instruments,  and  for  those  alone.  If  the 
magnet  is  kept  on  too  long,  the  currents  induced  in 
the  metallic  body  make  the  latter  hot,  and  for  this 
reason  the  magnet  should  be  used  only  for  brief  seances. 
Bergonie  does  not  bring  forward  the  method  as  a  sub- 
stitute for  X-ray  localization,  but  simply  as  an  addition 
to  the  armamentarium  of  the  military  surgeon. 


APPENDIX  III 

Localization  from  a  Single  Photograph 

By  means  only  of  a  single  photograph  the  X-ray 
worker  may  be  enabled  to  ascertain  the  distance  of  the 
tube  from  the  plate  resting  on  the  skin  of  the  patient, 
and  the  depth  of  any  foreign  body  below  the  skin.  In 
order  to  carry  out  this  method  he  must  be  provided  with 
a  small  hollow  box  or  frame  having  a  cross  of  fine  wire 
at  the  top  and  another  similar  cross  at  the  bottom. 
The  intersections  of  the  wires  must  be  exactly  opposite 
one  another,  and  the  distance  between  them — i.e.,  the 
thickness  of  the  box — must  be  accurately  known. 
A  convenient  distance  is  20  mm.  This  box  rests  on  the 
patient's  skin.  The  tube  below  being  excited,  a  small 
fluorescent  screen  is  placed  on  the  upper  cross  wires 
of  the  box,  and  this  and  the  tube  are  moved  about  until 
the  shadow  of  the  lower  cross  is  seen  to  be  accurately 
superimposed  on  the  shadow  of  the  upper  cross.  Then 
it  is  known  that  the  radiating  point  on  the  target  of 
the  tube  must  be  situated  vertically  below.  A  little 
further  combined  adjustment  will  secure  that  the 
shadow  of  the  embedded  bullet  falls  accurately  in  a 
line  with  the  superimposed  crosses.  When  this  is 
obtained,  it  follows  that  the  two  crosses  and  the  bullet 
are  all  situated  in  a  direct  vertical  line  above  the  radiant 
point  of  the  tube  target.  The  skin  is  now  inked  at  the 
spot  where  the   lower   cross  rests  upon  it,  a  photo- 

61 


62     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

graphic  plate  is  placed  on  the  upper  part  of  the  box, 
and  the  tube  below  is  displaced  a  known  distance, 
60  mm.  for  example.  Save  for  this  adjustment  of 
the  tube,  everything  remains  as  it  was  before,  and  at 
this  point  one  photograph  is  taken. 

From  the  data  afforded  by  this  single  negative, 
the  distance  of  the  tube  from  the  patient's  skin,  upon 
which  the  lower  cross  rested,  and  also  the  depth  of 
the  bullet  can  be  ascertained.  On  developing  the 
negative,  it  will  be  observed  that  there  is  one  shadow 
of  the  cross  wires  which  has  suffered  no  parallax; 
this  is  the  one  upon  which  the  plate  was  actually 
~  resting.  The  other  cross  will  be  seen  as  displaced,  and 
the  distance  between  the  two  crosses  is  carefully 
measured  on  the  negative.  An  equall}-  careful  measure- 
ment is  made  of  the  distance  of  the  shadow  of  the 
bullet  from  the  centre  of  the  first  cross.  The  same 
measurements  can  be  made  directly  on  the  fluorescent 
screen  if  no  photograph  is  taken. 

In  the  annexed  diagram  (a),  T  represents  the  original 
position  of  the  tube,  and  D  the  displaced  position 
at  which  the  single  photograph  is  taken.  The  distance 
of  the  tube  from  the  patient's  skin  (which  has  to  be 
found)  is  TS,  and  the  distance  of  the  bullet  beneath 
the  skin  (also  to  be  found)  is  SB.  The  distance  be- 
tween the  two  cross  wires  in  the  frame  is  represented 
by  CS,  and  the  direct  vertical  line  when  the  double 
cross  and  the  foreign  body  are  seen  in  superimposition 
is  represented  by  the  line  CSBT,  B  being  the  position 
of  the  foreign  body.  G  represents  the  displaced  image 
of  the  lower  cross  on  the  negative,  and  E  the  image 
of  the  foreign  body.  Diagram  [h)  shows  the  same 
displacements  on  the  fiat. 

From  these  data  the  following  can  be  ascertained: 


DIAGRAM. 
E  G     C 


Fluorescent  screen 
or  photographic 
plate  on  upper 
cross  wires. 


Lower  cross  wires 
resting  on  patient's 
skin  ;  or  on  couch 
if  distance  from 
tube  to  couch  is  to 
be  ascertained. 


■e- 


(b) 


T 

Fig.  38A. 


D 


(a) 


[To  face  p.  62. 


APPENDIX  III  63 

(i)  The  distance  of  the  tube  from  the  patient's 
skin. 

(2)  The  depth  of  the  bullet  beneath  the  skin  at  the 
point  already  marked  on  the  skin,  i.e.,  the  position 
of  the  lower  cross. 

The  matter  resolves  itself  into  a  simple  calculation, 
and  may  be  expressed  in  this  way: 

CG  -.CS  ::  TD  \TS 

The  distance  CG  is  measurable  on  the  negative,  and 
if   the  distance  CS  is  20  mm.,  and  the  distance  TD 

100  mm.,  then  TS=^       . — ,  and  gives  us  the  distance 

of  the  tube.  To  find  the  depth  of  the  bullet,  we  have 
the  following  equation : 

EC  :  [CS+BS]  ::TD:TS  -BS 
EC  {TS-BS)  =  TD  (CS+BS) 

The  distance  EC  is  measurable  on  the  negative,  and 
if  CS  is  again  20  mm.,  and  TD  100  mm.,  while  the 
distance  TS  is  known  from  the  previous  calculation, 
the  distance  BS  is  readilj^  discoverable. 


APPENDIX  IV 

The  Rectification  of  the  Current  supplied  to  the  X-Ray 

Tubei 

In  the  earh'  daj^s  of  X-ray  work^  the  currents 
emploj^ed  to  excite  the  tube  were  so  weak  that  the 
disturbance  and  difficulty  caused  by  the  inverse  or 
"  make  "  current  did  not  arise.  When  strong  currents 
came  to  be  used,  however,  this  *'  make "  current 
became  a  source  of  trouble  and  anxiety  to  X-ray 
workers.  Valve  tubes  are  largely  used  to  overcome 
the  difficulty,  but  these  in  themselves  are  subject  to 
disturbances. 

Since  the  major  part  of  this  book  was  written,  the 
author  has  constructed  a  device  in  the  shape  of  a 
commutator  attachment  for  bringing  about  the 
rectification  of  the  induction-coil  currents.  Being 
much  troubled  by  the  easy  reversal  of  his  tubes  when 
trying  to  get  rapid  exposures,  and  not  possessing  a 
Snook  apparatus,  which  embodies  a  rectifying  device 
for  making  an  alternating  current  unidirectional 
through  the  tube,  he  set  about  some  means  of  trying 
to  overcome  the  inverse  current  difficulty.  The  re- 
sult is  a  device  which  is  so  extremely  simple  that  it 
seems  incredible  that  it  should  not  have  been  worked 
out  before. 

^  Being  the  substance  of  a  communication  made  by  the  author 
to  the  Electrotherapeutic  Section  of  the  Ro3'al  Society  of  Medicine 
on  January  21,  1916. 

64 


APPENDIX  IV  65 

At  first  it  seemed  advisable  to  try  to  prevent  the 
production  of  the  inverse  current  rather  than  to  stop 
it  after  production,  as  in  Dr.  Reginald  Morton's  or 
Mr.  Miller's  arrangement.  With  this  object  in  view 
the  author  attached  to  the  spindle  of  his  little  rotary 
dipper  interrupter  a  series  of  studs  connected  with 
resistances,  and  so  arranged  in  relation  to  the  position 
of  the  blade  that  when  the  blade  was  just  dipping 
into  the  mercury  to  close  the  circuit  in  the  primary, 
the  finger  attachment  pressing  on  one  of  its  sides 
introduced  into  the  primary  circuit  a  resistance  of 
from  40  to  60  ohms.  As  it  rotated,  it  came  on  to 
other  studs,  and  gradually  cut  out  the  resistance, 
until,  just  before  the  break,  there  was  no  resistance 
interposing  at  all.  As  the  output  in  the  secondary 
is  a  function  of  the  rate  of  change  of  the  primary,  this 
gradual  building  up  of  the  saturation  of  the  primary 
through  these  resistances  resulted  in  no  inverse  current 
b)eing  passed,  and  an  X-ray  tube,  which  would  readily 
allow  inverse  current  to  pass  if  such  current  existed, 
showed  no  signs  of  it  at  all  when  worked  with  this 
arrangement. 

This  led  immediately  to  the  consideration  that  it 
would  be  still  better  if  this  ''  make  "  current  could  be 
utilized  by  being  passed  in  the  right  direction  through 
the  tube.  As  a  preliminary  to  the  construction  of  a 
commutator  for  this  purpose,  several  experiments 
were  carried  out  with  the  interrupter  in  order  to 
determine  whether  there  was  any  appreciable  lag 
between  the  moment  of  make  and  the  occurrence  of 
the  make  current  in  the  secondary.  To  one  of  the 
author's  interrupters  which  had  the  spindle  prolonged, 
a  disc  of  cardboard  was  attached  so  that  it  rotated 
with  the  interrupter  itself.     This  disc  was  then  marked 

5 


66     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

at  a  certain  point  corresponding  to  the  position  of 
the  dipper  blade.  The  interrupter  was  coupled  up 
to  a  lo-inch  coil  in  the  usual  way,  and  two  wires  were 
brought  from  the  secondary  terminals  of  the  coil  and 
fixed  on  either  side  near  the  periphery  of  the  disc. 
X^Hien  the  interrupter  was  started,  and  the  current 
sent  through  the  coil,  there  was  a  series  of  sparks 
from  the  secondary  terminals,  which  punctured  the 
cardboard  as  the  latter  rotated.  Punctures  were 
obtained  in  this  way  for  the  *'  make  "  and  "  break  '^ 
currents,  and  their  exact  position  was  ascertained. 
The  make  and  break  were  found  to  be  practically 
instantaneous,  and  with  the  blade  employed  it  was 
found  possible  to  obtain  an  angle  of  separation  of  very 
nearly  i8o  degrees. 

The  question  then  became  one  merely  of  com- 
mutating  these  currents  in  the  most  convenient 
manner.  In  1898,  when  devising  a  stereoscopic 
fiuoroscope,  the  author  employed  a  commutator  for 
the  current  from  the  induction  coil,  using  in  that  case 
a  vulcanite  disc  with  a  metal  spoke  or  radius,  and  so 
diverted  the  currents  which  were  to  illuminate  each 
tube  alternately.  Commutation  can  certainly  be 
carried  out  quite  simply.  The  method  the  author 
has  adopted  in  the  present  instance  is  to  attach  to 
the  prolonged  spindle  of  his  interrupter  an  insulating 
rod  about  10  inches  long,  made  of  wood  or  vulcanite. 
From  each  extremity  of  this  insulating  rod  projects 
a  light,  rigid  metal  rod  or  wire,  about  8  or  10  inches 
in  length.  To  each  end  of  these  fingers,  which  have 
insulated  bearings,  are  attached  the  secondar}'-  ter- 
minals of  the  coil  by  rubbing  contact.  Further,  these 
rotating  .terminals  of  the  secondary  coil — which  is 
what  the  fingers  really  become — are  adjusted  to  be 
parallel  to  the  dipper  blade,  so  that  if  these  fingers 


APPENDIX  IV  67 

are  pointing  vertically  downwards,  then  the  dipper 
blade  is  also  pointing  vertically  downwards  and  into 
the  mercury;  and  as  they  rotate  together,  they  always 
maintain  the  same  relative  position.  The  next  thing 
was  to  ascertain  the  exact  position  occupied  by  these 
fingers  at  the  moment  when  the  dipper  blade  was 
dipping  into  the  mercury.  This  was  easily  done  by 
putting  a  little  milliamperemeter  into  the  circuit 
with  a  dry  cell  and  turning  round  the  revolving  part 
until  the  meter  indicated  the  current.  At  this  point 
two  supports,  curved  so  as  to  represent  the  arc  of  a 
circle,  were  introduced,  the  fingers  forming  the  radius, 
but  with  a  clear  space  between  the  extremity  of  the 
fingers  and  the  supports.  Strips  of  metal  lined  these 
supports  on  their  inner  face,  and  they  were  electrically 
connected  to  the  terminal  to  which  the  wires  from 
the  tube  were  attached.  As  the  interrupter  rotated, 
the  current  through  the  milliamperemeter  remained 
constant  until  the  blade  came  out  of  the  mercury 
Just  at  that  point  the  fingers  were  rotated  at  a  con- 
siderable angle  to  the  other  side,  and  here  the  con- 
centric arcs  of  the  circle  with  the  metal  lining  were 
fixed,  and  to  these  the  break  discharge  sparked. 
Insulated  wire  was  carried  from  this  point  to  the  break 
take-offs  in  a  diagonal  direction.  By  this  simple 
construction,  when  the  interrupter  is  started,  and  the 
current  in  the  primary  turned  on,  the  tube  is  illumi- 
nated by  the  "  make  "  or  inverse  current  as  well  as 
by  the  "  break  "  or  direct  current  of  the  coil.  If 
the  two  take-offs  of  the  "  break  "  current  are  con- 
nected together  by  wire,  and  the  wire  to  the  tube 
allowed  to  come  only  from  the  ''  make  "-current 
take-off,  the  tube  will  be  found  to  be  quite  well  excited 
by  the  "  make  "  current  alone.  With  this  arrange- 
ment,   when   the    "  make "    current    alone   is   passed 


68     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

through  a  low-resistance  tube,  a  current  of  2  milH- 
amperes  is  obtained.  When  the  wires  from  the  coil 
are  connected  directly  to  the  tube,  so  that  the  com- 
mutator is  entirely  cut  out,  a  little  over  4  milliamperes 
is  registered,  but  owing  to  the  inverse  current  getting 
through,  the  needle  vibrates  so  as  to  make  the  reading 
a  little  indefinite,  and  the  tube  presents  a  remarkable 
appearance  of  unevenness. 

Hitherto  the  "  make  "  current  has  been  a  source 
of  serious  wastage,  not  to  speak  of  damage  to  the 
tubes  and  embarrassment  to  the  worker.  With  the 
arrangement  just  described,  it  may  be  hoped  that 
the  wastage  will  be  stopped,  and  that  whatever 
"  make  "  current  may  exist  in  any  given  coil  will,  sa 
far  as  it  is  effective,  go  through  the  tube  in  the  right 
direction  and  increase  its  output.  The  different 
appearance  presented  by  a  low  tube  when  worked  in 
the  ordinary  way,  illuminating  very  badly,  and  giving, 
of  course,  unsatisfactory  photographic  results,  as 
compared  with  the  appearance  presented  when  the 
commutator  is  attached  to  the  interrupter,  resulting 
in  a  unidirectional  current,  is  very  striking.  This 
apparatus  should  enable  the  ordinary  induction  coil 
to  compete  favourably  with  the  Snook  apparatus, 
which  hitherto  has  been  the  most  powerful  means  of 
exciting  the  X-ray  tube. 

Should  it  be  found  that  the  "  make "  current^ 
from  its  lower  voltage,  heats  the  tube  without  a 
corresponding  gain  in  increased  X-ray  output,  it  is 
quite  easy  to  join  the  "  make  "  take-offs  with  a  wire 
and — cutting  the  crossed  commutating  wires — join 
them  directly  to  the  X-ray  tube.  In  this  way  the 
tube  would  be  excited  only  by  the  usual  strong 
"  break  "  current  from  the  coil. 


APPENDIX  V 

Rules  for  the  Protection  of  X-Ray  Operators 

The  Rontgen  Society  has  made  the  following  re- 
commendations for  the  protection  of  X-ray  operators : 

The  harmful  effects  produced  by  X  rays  are  cumu- 
lative, and  do  not  generally  appear  until  some  weeks 
or  months  after  the  damage  has  been  done.  It  is  to 
be  noted  that  X  rays  of  any  degree  of  hardness  are 
capable  of  producing  ill  effects,  although  it  is  commonly 
supposed  that  soft  rays  only  are  harmful. 

It  is  undesirable  that  any  X-ray  treatment  should  be 
carried  out  except  under  the  direction  of  a  qualified 
medical  practitioner  experienced  in  X-ray  work. 

All  X-ray  tubes  must  be  provided,  when  in  use,  with 
a  protecting  shield  or  cover  which  prevents  the  access 
of  rays  to  the  operators  and  which  encloses  the  tube, 
leaving  an  adjustable  opening  only  sufficiently  large 
to  allow  the  passage  of  a  sheaf  of  rays  of  the  size 
necessary  for  the  work  in  hand.  Even  with  this 
shielding  the  operator  may  not  be  completely  pro- 
tected in  all  cases  (e.g.,  especially  in  screen  work), 
and  the  use  of  movable  screens,  gloves,  and  aprons 
is  recommended. 

Operators  should  be  warned  that  shields  obtainable 
commercially  are  often  ineffective,  and  tests  of  their 
opacity  should  be  made. 

Whenever   possible   the  cubicle   system   should  be 

69 


79     LOCALIZATION  BY  X  RAYS  AND  STEREOSCOPY 

used  for  X-ray  treatment  and  the  operator  should  be 
able  to  make  all  adjustments  from  a  protected  space. 

When  screen  examination  is  required  it  is  essential 
that  the  screen  should  be  covered  with  thick  lead 
glass  of  proved  opacity  and  that  the  screen  should  be 
independently  supported  and  not  held  in  the  hands 
of  the  operator.  If  the  hands  are  so  used  they  should 
be  properly  protected. 

The  hand  or  any  portion  of  the  body  of  the  operator 
should  never  be  used  to  test  the  hardness  or  quality 
of  the  X-ray  tube;  any  simple  form  of  penetrometer 
can  be  easily  arranged  for  this  purpose. 


APPENDIX  VI 

Plates  Illustrating  Special  Cases  (from  Stereoscopic  X-Ray  Photographs). 

PLAI  E  XVI. 


Fig.  39. — Fragment  of  Bomb  in  the  Knee^  precisely  located  and 
successfully  removed. 

The  piece  of  wire  represents  the  position  of  tlie  entrance  wound. 


1 

Fig.  40  — A  Rifle  Bullet  lodged  Very  Near  to  the  Second  Lumbar 
Vertebra,  on  its  Left  Side. 


This  was  successfully  removed  by  Mr.  Sherren. 


PLATE  XVII. 


Fig.  41. — Gunshot  Wound  in  the  P'oot. 

This  illustrates  the  advantage  of  stereoscopic  work,  or  it  is  possible  by  means  of  the 
stereoscope  to  see  the  position  occupied  by  each  shot  in  relation  to  the  bones  of 
the  foot. 


Fig.  42. — A  Needle  lodged  in  a  Girl's  Knee. 

In  this  case,  on  the  information  afforded  by  a  single  {i.e.,  a  non-stereoscopic) 
photograph,  an  attempt  had  been  made  to  remove  the  foreign  body  from  the 
front  part  of  the  knee  ;  but  the  stereoscopic  picture  showed  conclusively  that 
it  was  situated  at  the  back  of  the  knee.  Cross  wires  placed  on  skin  behind  the 
knee. 


PLATE  XVIII. 


Fig.  43. — Fracture  of  the  Jaw,  plainly  visible  in  the  Stereoscope. 


/ 


Fig. 


44- 


The  above  represents  a  particularly  interesting  case.  A  lady  had  trod  upon  a 
needle,  which  broke  in  the  foot,  and  from  a  single  photograph  an  abortive 
attempt  at  removal  was  made.  On  a  stereoscopic  record  being  made,  the  two 
bits  of  needle  were  found  embedded  in  the  first  metatarsal  bone  During  the 
operation  for  removal  a  bent  probe  was  introduced  into  the  wound,  the  head 
being  placed  close  to  the  position  where  the  fragments  were  believed  to  lie,  and 
this  stereoscopic  picture  was  taken.     The  fragments  were  successfullv  removed. 


PLATE  XIX. 


Fig.  45. — A  Fragment  of  Shell  in  the  Left  Thigh. 

The  wire  loop  was  put  on  the  wound  of  entrance  ;  the  smaller  cross  of  fuse  wire 
was  placed  on  the  back  of  the  thigh,  and  the  large  cross  on  the  front. 
The  stereoscope  reveals  their  relative  positions  to  the  piece  of  shell,  which  latter 
was  successfully  removed. 


Fig.  46. — A  Bullet  successfully    located  between  the  Scapula 

AND  THE  Ribs. 


PLATE  XX. 


Fig.  47. 

One  of  the  earliest  cases  in  which  a  stereoscopic  photograph  was  secured  of  the 
female  pelvis,  with  the  ureter  (the  left)  catheterized,  and  a  wire  introduced  into 
the  hollow  catheter.  This  was  done,  at  the  author's  request,  by  Mr.  Hurry 
Fenwick.    A  small  opaque  gland  is  seen  lying  close  to,  but  outside,  the  ureter. 


Fig.  48. — A  Stereoscopic  View  showing  Teeth,  Antrum,  and 
Frontal  Sinuses. 


PLATE  XXI. 


Fig.  49. — A  Shrapnel  Bullet  situated  above  the  Hip-Joint. 
Its  exact  position  was  indicated  to  the  surgeon,  and  it  was  easily  removed. 


Fig.  50. — A  Piece  of  Shell  situated  near  the  Trochanter  jMajor- 

LOCATED  and   EASILY  REMOVED. 


PLATE  XXII. 


Fig.  51. — Stereoscopic  Photograph  of  Eye,  showing  Three  Small 

Specks  of  Lead. 

In  this  case  a  rifle  bullet  had  hit  something  in  the  trench  and  split  up,  and  these 
minute  fragments  went  in  the  eye  at  one  point  of  entrance.  The  point  of  the 
indicator  wire  is  very  close  to  the  wound  of  entrance,  visible  in  the  eyeball. 


Fig.  52. 

The  above  photograph  represents  the  case  of  a  Belgian  officer  who  had  a  small  scar 
in  the  upper  eyelid,  near  inner  and  upper  border  of  right  orbit.  He  com- 
plained of  persistent  headaches.  On  X-ray  examination  it  was  fourid  that  a 
fragment  of  high-explosive  shell  had  passed  through  to  the  left  orbit.  This 
was  precisely  located  and  easily  removed  by  Mr.  Armour,  with  complete 
recovery.  The  use  of  the  telephone  (see  p.  55)  greatly  facilitated  the  procedure 
of  extraction.  In  this  illustration  the  lower  end  of  the  wire,  which  is  fastened 
to  the  patient's  forehead,  rests  on  the  wound  of  entrance. 


PLATE  XXIII. 


Fig. 


53- 


In  this  case  a  rifle  bullet  struck  the  patient's  own  rifle,  and  small  particles  injured 
both  eyes.  Some  lodged  in  the  left  eyeball,  and  had  to  be  removed,  and  the 
above  is  the  stereoscopic  picture  of  the  right  eye,  showing  some  extremely 
minute  particles  which  were  located  just  outside  the  eyeball,  probably  resting 
upon,  or  against   the  sclerotic 


Fig. 


54- 


The  case  illustrated  above  is  fully  described  on  p.  52.  The  wire  is  on  the  lower 
right  eyelid.  The  shot  is  external  to  the  sclerotic,  below  it,  and  on  the  nasal 
side. 


PLATE  XXV. 


Fig,  57. — Piece  of  High-Explosive  Shell  ix  Orbit. 


Fig.  58. 

Tne  above  represents  the  case  of  an  officer  who  was  injured  in  both  eyes  by  the 
fine  sputter  of  a  broken-up  German  bullet.  One  eye  was  removed,  and  the 
other  was  so  defective  that  there  was  great  difficulty  in  being  kept  steady 
while  being  X-rayed.  Therefore,  the  loop  made  of  thick  fuse  wire  was  held 
firmly  against  the  slightly  open  eyelid,  and  the  eyeball  was  thereby  fixed  during 
the  exposure.  It  was  so  placed  that  the  centre  of  the  cornea  was  situated  in 
the  centre  loop.  On  looking  at  this  in  the  stereoscope,  the  loop  standing  out 
in  relief  will  indicate  the  position,  and  it  will  be  quite  plain  that  there  are 
two  metal  particles  inside  the  eyeball.  These  could  be  seen  subsequently 
scintillating  with  the  ophthalmoscope. 


PLATE  XXVI. 


™ 


Fig.  59- — The  Coolidge  Tube  in  Action. 


^ 


Fig.  6o. — Pinhole  Photograph 
OF    Coolidge    Tube  :    Side 

View. 


Fig.  6i. — Pinhole  Photograph 
OF  Ordinary  X-Ray  Tube  : 
Side  View. 


Note:  The  pinhole  stereoscopic  view  of  the  Cooh'dge  tube  in  action,  represented 
above,  was  taken  with  30  seconds'  exposure,  while  r  ma.  of  current  was  passing 
through  the  tube.  The  circular  focus  on  the  target  or  anticathode  is  represented 
as  a  round  spot  of  great  density,  but  the  whole  of  the  target,  even  to  the  tapering 
end  of  the  support,  is  shown  to  be  giving  off  X  rays.  The  rim  of  the  cathode 
above  is  shown  to  be  producing  X  rays,  though  more  feebly.  The  special  X-ray 
plate  employed  was  protected  in  the  usual  opaque  envelopes,  so  that  no  effect  can 
be  ascribed  to  stray  light.  When  the  tube  was  turned  so  as  to  present  a  view  of  the 
back  of  the  anode,  a  pinhole  photograph  again  showed  the  X-ray  effect  in  this 
region,  and  when  the  experiments  were  repeated  with  the  plate  wrapped  in  tinfoil, 
although  the  action  was  enfeebled,  the  enfeebling  was  relative,  and  the  rays  from 
behind  the  anode  were  as  penetrative  as  before.  It  should  be  added  that 
Mr.  Coolidge  has  made  a  hooded  tube  to  obviate  these  distributed  rays.  Fig.  61 
is  introduced  for  comparison  to  show  a  pinhole  photograph  of  the  ordinary  tube, 
20  minutes'  exposure,  i  ma.  passing  through  the  tube.  The  Coolidge  tube  (Fig.  60) , 
taken  under  identical  conditions,  shows  less  rays  from  the  glass  bulb,  but  a  larger 
diffusion  over  the  surface  of  the  target.  The  long  exposure  of  20  minutes  was 
given  in  order  to  detect  the  feeble  secondary  rays  from  the  glass  surface  of  the 
tubes. 


INDEX 


Akode,  position  of,  3 
Atomic  weight  and  X-ray  pene- 
tration, II,  24 

Barium  platinocyanide  screens,  13 
Bergonie,  Professor,  59 
Binocular  vision,  15,  44 
Bismuth  ointment  on  skin  to  show 

stereoscopic  effect,  45 
Break,    rotary,    commutator    for 

use  with,  56 
Brewster,  Sir  David,  15 

stereoscope,    19 
Bullet,  localization  of,  33 

Cathode  focus,  3 

rays,  2,  9 
Christie,  A.  C,  37 
Commutator  for  use  with  break,  66 
Coolidge  tube,  5 

Co-ordinates   and   planes   of    ref- 
erence, 31 
Couch,  a  new  X-ray,  22 
Cross-thread  localizer,  33 
Cross  wires  in  front  of  tube,  3 

Diaphragms,  9 

Double-exposure  photographs,  37 

Eddy  currents,  60 

Electromagnet  as  aid  to  localiza- 
tion, 59 

Eyeball  and  orbit,  foreign  bodies 
in,  47 

Fluorescent  screen,  13 

measurement  on  the,  25 
stereoscopy  and  the,  20 

Focus  of  cathode  rays,  3 

Foreign  bodies   detectable   by  X 
rays,  24 
in  eyeball  and  orbit,  47 

Freimd  of  Vienna,  10 

Geometrical  considerations  in 
localization,  29 


Glass    of    tube,    secondary    rays 

from,  7 
Gloves,  X-ray,  12 
Graham  Bell  and  telephone,  55 
Gynaecology,  X-ray  measurements 

in,  45 

Hampson,  Dr.  Wilham,  28 

"  Hard  "  X  rays,  5 

Hardness  of  tube,  a  test  for  the,  5 

Headpiece,  use  of,  in  eye  locaUza- 

tion,  47 
Holland,  Captain  Thurstan,  29 

Induction  coil,  5 

rectifying  currents  from 
the,  64 

Lead  as  a  protective  substance,  1 1 

screens,   12 
Le  Conte,  Joseph,  LL.D.,  15 
Localization,  conditions  for,  24 

from  a  single  photograph,  61 

precise,  29 

rapid,  22 

Mackenzie  Davidson  cross-thread 
localizer,'  34 

Magnetizable  foreign  bodies,  local- 
ization of,  60 

Needle,  localization  of,  40,  45 
Negative,  interpreting  the,  33 
Nitrate  of  silver  for  skin-marking, 
44 

Ophthalmic  surgerj^  use  of  tele- 
phone in,  58 
Ophthalmology,  X  rays  in,  47 
Orbit,  foreign  bodies  in,  47 

Paracathodic  ra^^s,  10 
Parallax,  effect  of,  35 
Pelvis,  to  ascertain  size  of,  45 
Photography  of  screen  images,  13 
Pinhole  photography  of  anode,  3,  4 
Plumb-bob,    use  of,  for  centring, 
17 


72 


INDEX 


Projection,  central  and  parallel,  29 
Protective  devices,  10,  69 

Rapid  X-ray  localization,  22 
Rectifying  induction-coil  currents, 

64 
Rontgen,  Professor,  5 
Rules  for  protection  of  operators,  69 

Screen     examination,     protection 

for,  13 
Screen  images,  photography  of,  13 
stereoscopic  view  of,  20 
localization,  42 
localizer,  rapid,  26 
measurement  on  the,  25 
Screens    of     lead    for    protective 

purposes,  12 
Secondary  rays,  7 

nature  of,  9 

physiological    action    of, 
II 
Single  picture,  misleading  nature 

of,  14 
Skin-burns  due  to  X  rays,  10 


Snook  apparatus,  64 
Stereoscopic  result  of  localization 
method,  43,  51 
screen  images,  20 
Stereoscopy,  X-ray,  14 
Surgery,  use  of  telephone  in,  55 

Telephone  attachment  in  surgery, 

55 
Therapeutics,  secondary  rays  in,  10 
Thompson,  Professor  Silvanus,  10 
Tube,  construction  of,  2 
Tungsten  for  cathode  terminal,  5 

Vertical  ray,  16,  25 

Visual  axes,  convergence  of,  51 

Wheatstone,  Sir  C,  15 
stereoscope,  18,  51 
Wire  loop  for  eye  fixation,  49 


X-ray  stereoscopy,  14 

tube,  construction  of,  2 
X  rays,   "  hardness  "  and 
ness  "  of,  5 


soft- 


LEWIS   AND   CO.,    LTD.,    I36    GOWER    STREET,    LONDON,    W.C. 


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